Internet Problem Solving Contest

IPSC 2010

Problem M – Mass psychoanalysis

Note. This is a special problem. No points can be gained for this problem.
The only thing you can gain is negative penalty time.

In Asimov’s famous series of books on the Foundation one of the main characters, Hari Seldon, is credited with inventing psychohistory: a scientific discipline that can use statistics to predict the behavior of large groups of people. We are now asking you to lay the foundations of psychohistory for real. Your goal is to predict the behavior of your fellow contestants as good as you can.

We will be playing a simple game. In the game you have a single submit. You can use this submit at any point during the game. If you do so, we will record the exact time between the start of the game and the moment of your submission. During the game these submits are not shown in the standings.

Once the game is over, we will then compute the average of all the submission times. Your goal in this game: your time must be as close as possible to two thirds of that average.


Three teams take part in the game. The first team submits 500 seconds after the game starts, the second team submits at 600 seconds and the third one at 1690 seconds.

The average submission time is (500 + 600 + 1690)3 = 27903 = 930 seconds. Two thirds of that average is 930 (23) = 620. The second team’s submission time is closest to 620.

Input specification

You may submit anything you wish to (e.g., an empty file). The content of your submission does not matter, only the time is important.

The first game starts at the beginning of the contest and ends after two hours. During these two hours you may submit the easy data set M1 in order to play this game.

After two hours the first round will be evaluated and the results will be made public.

The second game starts at 2h30 and ends at 4h30 into the contest. (I.e., it starts in the middle of the contest and ends 30 minutes before its end.) During these two hours you may submit the hard data set M2 in order to play this game. (Note that the time you choose is the time since the beginning of the game, not the beginning of the contest.)

After the second game ends, it will be evaluated and the results will be made public.


In the first game the following scoring is used. For each team only the best option applies.

In the second game the scoring will be double (i.e., -240 for an exact guess, etc.).