For given integer N (1<=N<=10^4) find amount of positive numbers not greater than N that coprime with N. Let us call two positive integers (say, A and B, for ex...

Mary is a teacher in a middle school and she has a table seat storing students’ names and their corresponding seat ids.

For given number N you must output amount of N-digit numbers, such, that last digits of their square is equal to 987654321.

It is not easy to prepare a problem for a programming contest. Petya and Vasya decided that problem “A+B” needs at least n distinct solutions to be written. It ...

First year of new millenium is gone away. In commemoration of it write a program that finds the name of the day of the week for any date in 2001.

Famous Berland ACM-ICPC team Anisovka consists of three programmers: Andrew, Michael and Ilya. A long time ago, during the first few months the team was founded...

You are given natural number X. Find such maximum integer number that it square is not greater than X.

Along the border between states A and B there are N defence outposts. For every outpost k, the interval [Ak,Bk] which is guarded by it is known. Because of fina...

Vasya learned definition of median of three numbers. He says, “Median of three numbers is the number located in the middle when numbers are ordered in non-desce...

On a circle border there are 2k different points A1, A2, …, A2k, located contiguously. These points connect k chords so that each of points A1, A2, …, A2k is th...