Shalom to Ning

I had never expected that Feb 19, 2017 would be the last day we say farewell to each.

Red Sea from Eilat

We used to talk about math puzzles, from blue-eyed islander puzzle to the hardest logic puzzle ever, every time on the bus from or to Shuk. We joked about the possibility that the apple cores we throw in the Carmel national park would one day become apple trees. We had plans to host a hot-pot party and introduce Mahjong to our Israeli friends…

I realized that all these can only expressed in past tense when I saw you forever asleep in Eilat.

We were so close, yet we are so far apart.


First week in Israel

Here is a list of things I have experienced during the first week in Israel and some tips for those of you who plan to visit me in Haifa!

Hainan airline has a direct flight from Beijing to Tel Aviv, and they have a resting area for transiting passengers in Beijing.

If this is your first time in Israel, make sure your arrival day is not Saturday or any holiday. Saturday (or holiday) means almost no public transportation, almost no restaurants and fewer people on the street whom you can ask help from.

Most Israelis are quite friendly and speak decent English. Even if someone does not speak English at all, he or she is always able to grab someone closeby to help.

You can exchange all major currencies (eg. US dollars, Chinese yuan) for new Israeli shekels at the airport in Tel Aviv at Bank Hapoalim. Expectedly, the rate is not as good as what you can get outside the airport. A lot of places accept major credit cards, such as Visa and Mastercard. Some places ask for a purchase of 20 shekels or more if you use credit card.

The vending machines for train tickets did not accept my Mastercard. The ticket from the airport to Haifa (Hof Hacarmel station) costs 35 shekels. The train is on platform 2 and it has WiFi connection. Use Google map to tell which station you are arriving if you, like myself, do not understand enough Hebrew.

The train from Tel Aviv to Haifa goes along the coastal line of the mediterranean sea. Highway no.2 lies between the rails and the coast, which resembles highway no.1 in California.

Bus no.11 goes from Hof Hacarmel to Technion. The bus fare is something slightly less than 6 shekels. Moovit is a must for public transportation planning, and it can send you notification when you are approaching at your destination.

Uber and Lyft do not have services in Haifa (but Uber does in Tel Aviv). People use Gett (aka Get Taxi) to call cabs. Since tipping is not required for taxi, remember to turn off automatic tipping in the app. You can use my code GTMLIYK for 15 shekels off your 1st ride.

The most popular messaging app is WhatsApp. I was asked for my WhatsApp contact for quite a few times.

Google Fi (global cellular service including data) works quite well in Israel. For the first week, I’ve heavily relied on my smart phone for navigation, transportation and information retrieving. It’s probably a good idea to carry a power bank. The outlet sockets in Israel are Type C and H.

Mediterranean sea from Hof Hacarmel.

Other random observations:

On Sunday, the train is full of soldiers. A few were probably carrying M4 carbines when I was on the train.

The rent for the property listed online (eg. or Facebook group) usually does not include city tax and building management fee.

Some apartments in Haifa have a separate room for the toilet only.

You give all the checks for the rent to the landlord when you sign the contract. Technion is able to write a guarantee letter to the landlord saying that they will freeze your last payment as the security deposit.

You will not be able to change the PIN, set by the bank, of your debit card, at least for Bank Leumi, the other major bank in Israel besides Bank Hapoalim.

Hebrew calendar and Chinese calendar are both lunisolar, so they are similar in a lot of ways. Friday and Saturday are weekends in Israel.

High schoolers can choose how difficult the math they want to learn. For example, calculus (including formulas like e^{i\theta} = \cos \theta + i\sin\theta) is offered in high schools.

However, most high school graduates need to go to army for 2-3 years and it’s hard to recall what they have learnt after the army. Top students might have the option to delay their military service.

Pork and shellfish are not Kosher, so you will not be able to see them in most supermarkets. It is also not Kosher to eat meat with milk.












我走路来到学校,一路上,随身听里放着周杰伦的龙卷风。这首歌是初中时候第一次接触流行音乐时听的,从此一盘盘磁带,一张张 CD,陪伴着青春。我跟着哼唱,爱情来得太快就像龙卷风……



上午一晃而过,中午去学校食堂的路上,遇到一群在把网球当足球踢的本科生。我心想还是踢瓶盖更环保一些。又走不远,另外一群孩子拿着 iPhone 和 iPad 正在玩部落战争。这简直太逊了,初中班级里发明的拍手游戏变化多端、风靡全年级,游戏平衡性和竞技性岂是这些触屏上的游戏能比拟的。我边走边骄傲地想,这些都应该进入世界文化遗产名录。


关上微博,在办公室工作了几个小时后,学院里的研究生和教授开始纷纷回家,预备享受周末。英语里 TGIF 的意思是 Thank God It’s Friday (感谢上帝今天是周五),当地人一般都会去酒吧消遣,但我还是同几位当年的球友约定在学校的篮球场感谢上帝。我们今天约了和另外一组美籍华人打全场对抗,虽然没有什么人围观,但我们还是非常认真地对待。对方有几个球员的个人能力非常厉害,但我方毕竟一起磨练多年,不用看就知道队友的位置。突破,分球,倒到圈顶,三分球进了。这是我们常用的战术,而且变化很多。包夹,盗球,抢篮板,盖帽,后仰跳投,每个人都有自己的擅长。汗水挥洒在篮球场上,没有人记得比分。


我回到自己的公寓,仰面躺在床上,想起了当年初中住宿夜聊室友彻夜讲述《神雕侠侣》,想起上课吃橙子听 CD 纷纷被老师发现没收,想起笑容依旧挂在那一张张天真无邪的脸上,想起……








除了在 MOP 第三周举行的为时两天的 TSTST 以外,在前两周还有四次 MOP 测试和两次 IMO 模拟考试。这六次考试都是不关联来年的集训队选拔的。但这六次考试很有趣的是,阅卷员(大多数是过去参加过 IMO 的学生)会对解答主观地作出风格分的评判。比如,如果你的解答是一通暴算,那很抱歉,你的风格分可能会很低。为了鼓励第一次的参加的学员,特别是在红组和绿组的学员,他们的四次 MOP 测试会在原有的三个题目上附加两个简单的题目。

为了增进学生互相之间的合作,在前两周还有三个学生一组组队赛。红组和绿组用一套稍简单的题,蓝组和黑组用稍难的一套题。评分的方式是在阅卷员面前解释自己的解答。换句话说,在这个过程中,学生不但要解决问题,还要教会组里不会的伙伴。这正好也呼应了 Jane Street 讲座里所说的工作中的团队合作。

除了之前说的几个考试测验外,整个项目里还有一个广受同学欢迎的叫做 ELMO 的竞赛。ELMO 具体是什么意思不得而知,但每年这个名字都会有新的诠释。比如今年 ELMO 代表 Ego Loss (surely) Must Occur,意思就是损伤自尊心必然发生。这个竞赛由老生(Veteran,也就是至少是第二次参加 MOP 的学员)运作,模拟 IMO 的模式:老生提供试题,构成备选试题列表(ELMO Shortlist),新生(Rookie,第一次参加 MOP 的学员)组队,老生被分配到每队成为领队,新生参加比赛后由老生阅卷并互相之间协调分数。

虽然这个活动仅仅是一个由学生运行的比赛,但是每年他们都会像模像样地把试题和备选试题发到上篇提到的 Art of Problem Solving 的网站,不知道内情的人,乍一看肯定会觉得这是一个由某机构运作的官方的比赛。学生们拍照的时候不会说Cheese(茄子),而会喊 ELMO Meeting!(ELMO 会议),可见这个比赛的受欢迎程度。

除了这个 ELMO 竞赛外,另外有一件事情彻底颠覆了我之前对美国高中数学教育的刻板印象。有一天,教练和阅卷员开完会,回到寝室楼大厅,看到了这番情景。

Plank countdown.

为了说清楚这个比赛,简单讲一下美国的一个为初中生设计的竞赛 MathCounts。这个比赛类似于中国的华罗庚数学金杯赛,最后一轮是抢答赛(Countdown Round),也是该项比赛唯一的口试部分,用于决定每年的冠军。而照片里所看到的是高中生版本的 MathCounts,大家管它叫平板支撑抢答赛(Plank Countdown),因为比赛选手需要在抢答的过程中一直平板支撑。出乎我意料的是,孩子们的心算速度非常快。决赛轮,两个选手大多数时候都能在题目刚念完未念完的时候给出答案。

孩子们在不断创新的同时,整个教练组也尽力会去优化整个项目的体验。比如 Po-Shen 在第二周周五安排了一个叫哲学(Philosophy)的专题,学生分成四组和不同的教练和阅卷员答疑解惑“人生哲学问题”。在最后一周给 TSTST 阅卷的时候,教练组和阅卷员还讨论了是否要将试卷还给学生的事情。为了能让学生成长,最后决定最大限度地透明化,先将分数告诉学生,如果有异议可以和阅卷员讨论,待分数稳定后将试卷归还。这与近几年的做法很不相同。除此之外,还有一个类似座谈会性质的“超越 MOP”(Beyond MOP),所有人集中在 Neihardt 蓝色大厅一起你问我答。

在昨晚刚结束的学生才艺秀晚会中,负责人 Steve Dunbar 提到这次活动除了 D. E. Shaw & Co 和 Jane Street 赞助外,还有 Two Sigma,Dropbox,Citadel,Art of Problem Solving  以及最主要的赞助 Akamai Foundation。这些赞助公司有一个共同的特点,就是他们的创始人中都有数学竞赛的经历,并且很多曾经参加过 MOP,他们在社会上取得了成功之后不忘回馈。才艺秀结束后,两个阅卷员坐在走道里,给学生讲他们当年在 MOP 的时候的故事。其中 Brian 说了一个蛮有意思的故事是,当年,也是我高三那年,冯祖鸣带着美国队和中国队一起训练,结果美国队有个学生结识朋友的方式是把人抱起来,然后背着地摔地上,有人调侃说就因为这个中国队那年没拿团体第一。我相信这些有趣的轶事会一代一代传下去。

由于整个美国数学竞赛协会有人事变动,整个办公室将从内布拉斯加搬到华盛顿。今年是 MOP 在内布拉斯加哎的最后一年。今年恰逢 Po-Shen 被任命为了美国队领队,明年的 MOP 将在匹兹堡卡内基梅隆大学举办。





上个学期,不时会在午后太阳将下山前,在卡内基梅隆大学附近的山坡上小跑。有一次小跑归来,进入 Doherty 楼的时候,遇到了 Po-Shen Loh。我之前就听说 Po-Shen 是美国国际数学奥林匹克(下简称 IMO)队的副领队。Po-Shen 当时推着自行车,突然问我,你想不想今年暑假辅导美国 IMO 集训队。我回答说我非常乐意,但因为没有碰竞赛好多年,水平肯定不行了,但!是!平面几何肯定是可以保证质量的。于是,我就这么来到了内布拉斯加的首府林肯。

说到内布拉斯加,大多数美国人的反应是不毛之地(in the middle of no where),喜欢看生活大爆炸的同学肯定会说是 Penny 的老家。但林肯毕竟是首府,集训队住宿和上课的地方在内布拉斯加大学林肯分校。美国大学在校园建筑方面向来奢华,集训队所住的地方更是学校里历史最悠久的宿舍楼,条件可以说是非常舒适。

这个暑期项目的官方名字是 Maths Olympiad Summer Program,缩写就是 MOSP,但是大家喜欢管它叫 MOP,直译过来就是拖把,参加这个活动的学生也就自然被称之为了 Mopper,直译过来就是拖地的人。根据 Mopper 们在之前一年中各个竞赛的综合表现被分为黑组(十人)、蓝组(十五人)、绿组(十五人)和红组(十一人)。黑组的十个成员中包括了即将参加今年在非洲开普敦举行的 IMO 正式队员。

MOP 正式开始是从六月九日,在这之前还有给黑组成员的小灶 Pre-MOP。为了备课,我的母亲从上海帮我翻拍了很多以前的笔记和数学日志,精选了一百来个题目,花了不少时间把每一个题目都做了一遍,并翻译成英文写了解答。

即便如此备战,第一天试水还是被黑组的学生震撼到了。具体过程是这样的,由于种种原因,我没办法复印讲义,于是只能把题目抄到黑板上。我抄了五六个题到黑板上,心想,少年们,受苦吧!但离下课还有一会的时候,学生当中有一个叫 James Tao 问我有没有更多的问题,于是我又得往黑板上抄了两三个题目才稳住了局面。


Pre-MOP 很快就过去了。六月九日大批的蓝绿红组的学生到来,看面孔大多数都是华裔,不知道这算是人种优势,还是华人家长比较在数学教育。于是我问 James Tao 他是如何走上奥林匹克数学道路的。他说,一方面,是他父亲的辅导,小时候拿着一本中文的几何书翻译着将给他听。另一方面,他发现了 Art of Problem Solving 这个网站和一本叫 Problems from the Book 的书。我个人的看法是,华人家长会更有意识培养和挖掘孩子数学能力。

六月十日的晚上有一个简短的会,面向所有的 Mopper。先是活动的负责人,美国数学竞赛协会的 Steve Dunbar 先生讲了一些纪律方面的事情,接着 Po-Shen 讲了一番话,我觉得很值得回味。他说,因为鸽笼原理,不可能每一个人都能在学术圈找到教职。于是参加奥林匹克数学的孩子,将来会分散到各个行业,并且大多数成为各个行业的佼佼者,所以这个活动是一个很好的结识朋友的机会。

这个活动实际上不只是结识朋友的好机会,还是一个帮助学生扩展眼界的好机会。这次活动得到了 D. E. Shaw & Co. 的支持,所以整个活动的时间也可以更长。MOP 第一周除了 D. E. Shaw & Co. 有来演讲以外,周末还有 Jane Street 的人过来介绍他们的公司。我记得 Jane Street 的人开篇就说,希望这些搞奥林匹克数学的孩子能够离开自己舒适的圈子,去业界闯一闯。

除了不学术的这一面外,MOP 还有特别学术的一面。每两天晚上八点半都会有讨论班。讨论班由像我一样的教练给演讲,Po-Shen 要求说最好是和当前研究相关的,但更要容易理解。大多数教练,包括我,不是什么名师,而是过去在不同国家有竞赛经验的,有的工作了,有的在学术界。

更颠覆我预期的事,MOP 这个活动根本不是用来选拔最后去 IMO 比赛的!整个活动,只有一个叫 TSTST 的考试是算成绩的。TSTST 全称是 Team Selection Test Selection Test,也就是选拔参加国家队选拔考的考试。换句话说在这个考试里表现较好的学生(去年是十三人)可以参加来年的国家队选拔考试。

于是乎,MOP 和竞赛真正有关的只有:一、培训今年参加 IMO 竞赛的美国队队员;二、通过 TSTST 选拔合适的人选参加来年的 TST,并结合他们在来年的 USAMO 的成绩,决定美国国家队人选。

在我看来,这个策略是非常适合美国国情的。想象一下,在一个没有奥数产业的国家,本来美国人就对奥林匹克数学不感冒,再通过连续竞赛刷掉学生的方式选拔,很可能会进一步打击参与度。这些在 TSTST 中表现不错的学生,不但获取了自信,并且可以有很长时间准备来年的竞赛,继续进步成长,整个过程压力也会小一些。












Today, probably, is not my day. I dropped my phone on the ground when I was rushing to the first recitation. The screen was totally shattered into pieces. And I had no time mourning on the loss of my first smart phone because I had to arrive in the classroom on time.

Cobweb style for Halloween.

In the afternoon, I gave it a try at the Apple store. And unfortunately, I had to pay 200+ dollars for a replacement of my phone. As I was hesitating whether to take it or not, they told me that actually they could do nothing with the device because it is purchased outside the country. I left the Apple store with the number of Apple Care.

Then I gave my second try. The customer service whose name is Jeremy let me hold on the line for about 10 minutes because the case is rare and he was asking for help from the senior advisor. At first, he told me that probably I needed to send my phone back to China, get it fixed and send it back. And he transfered me to the customer service in China. After listening to about-10-minute enjoyable pop songs with no one answering the phone call, Jeremy told me that he had been looking for an alternative solution so that I wouldn’t have to go through the procedure in China.

Finally, he transfered me to the senior advisor whose name is Diego. And he found a new policy for devices purchased abroad which I thought was perfect for me. He charged me 99 dollars to upgrade my phone with an Apple care which will cover two incidents with 49 dollars extra charge each time. The only downside of this deal is that what I got is a new iPhone 5 locked to AT&T network instead of the factory unlocked one. I think overall it is a good deal because it’s cheaper and gives more protection.

During the evening, I went again into the Apple store, and replaced my phone with a new one. But I don’t know why it took them for like an hour to get it done. But anyway, it’s fixed.

Lesson learned. Buy a case. Just in case.



复旦附中 Just for you 跨校点歌祝福单




Legacy of Frank Lloyd Wright

Finally, I got a chance to visit Fallingwater, a house designed by Frank Lloyd Wright in 1935. I had long dreamed of this trip. And Wright didn’t let me down. As he is always right.

Fallingwater & Falling Water by Pan Liu

With narrow rooms inside, this house is organically designed so that people are ‘forced’ to come outside, to connect with the nature. On the other hand, we’ve seen rocks inside the living room and a corridor in the house, as an extension of the outside. This intertwined theme, the combination of nature and design, can be seen in every single dimension of this house.

Horizontal Rhythm Inside Out by Pan Liu

Another thing to notice is that Wright kept a uniformly horizontal rhythm in his design. The lines formed by shelves, tables, beds, etc. are aligned in such a paranoiac way. Even the stairs were designed without handrails so that the rhythm can be continued and extended.

Unfortunately, we only had the regular tour because the in-depth tour tickets were sold out when I was purchasing online. However, it gives me a good reason to see this place again. Maybe the brunch tour or the probably-overpriced sunset tour next time.


Con Man

I received the following email this afternoon.

I’m sorry I didn’t inform anyone about me and my family short trip to Madrid, Spain. Unfortunately we were mugged at gunpoint, at the hotel park we checked into. Our cell phone, cash and credit card was stolen in the process and we  immediately file a report to the Police, but they seems to be taking things too slow. Our flight leaves in few hrs from now and we need a quick loan to settle the hotel bills and our transport to the airport. I promise to reimburse immediately we arrive back home safely. Please get back to us asap.
—- —-

At first, it makes a little sense since I know this friend lives with his / her family. But it looks somehow suspicious, because apparently this friend can write in Chinese. And Gmail also popped up a message warning that the content of this message is suspicious. But I couldn’t rule out the possibility that he / she was really needing my help. So I replied:

I would definitely like to help you. Just to check it’s really you. Could you tell me who discovered the zero-one law?

One may ask more advanced questions, like personal questions. But usually you will get a vague answer.

Hi Roy,
I’m glad you replied back and am appreciative for your concern. It was a horrible experience but glad we were not physically injured. To answer your question, zero-one law was discovered by Ron Fagin. The total amount we are needing is about $2000, that will cover all our expenses to settle the bills and extra to return home. We don’t have any money left on us right now. You can have the money transferred on my name from any western union money transfer office around you.
Here’s my Info,
My passport name is under: —- —-
Nearest western union address: Plaza de Santa Ana 14, 28012 Madrid, Spain.
Please get back to me with the transfer confirmation number#. I’ll standby near a computer to check back.

Obviously, they failed. It’s Kolmogorov! Meanwhile, I saw the status of this friend on Chinese Facebook. Both his / her gmail and Facebook were hacked. So I decided to play with these con men for a bit while.

Sorry. That’s the wrong answer. I would definitely send you the money if I can verify it’s you. But you really need to tell me the right answer. Please try again. You should know the right answer. Take your time.

They replied promptly.

Oh Sorry, it’s Andrey Nikolaevich Kolmogorov.

That’s ridiculous! Who the hell can remember the middle name of Kolmogorov except Kolmogorov himself. So I replied politely with sarcasm.

Yes, that’s absolutely correct. Just one last question. You understand Chinese, right? Please tell me what’s the meaning of 你是骗子,我要报警 ? (Translation: you are a liar. I am going to call the police.)

I expected that they wouldn’t get back to me any more. But out of my expectation, they responded in Chinese!

它意味着你是愚蠢的不相信我在危险中。(Translation: It means you are stupid. Don’t believe I am in danger.)

This was astonishing. They even tried Google translate!
A quick reminder: there are several things you can do to protect your gmail or Facebook account before it’s too late. You can set up a strong password and use 2-step verification, though they might cause inconvenience sometimes.