Once in a forest, there lived N aggressive monkeys. At the beginning, they each does things in its own way and none of them knows each other. But monkeys can’t ...

现在有n个人，从1标号到n。同时有一些奇怪的约束条件，每个都形如：a必须在b之前。同时，社会是不平等的，这些人有的穷有的富。1号最富，2号第二富，以此类推。有钱人就贿赂负责人，所以他们有一些好处。...

Andrew has just made a breakthrough in sociology: he realized how to predict whether two persons will be good friends or not. It turns out that each person has ...

Find all pairs of prime numbers (A, B) such that A<=B and their sum is also a prime number and does not exceed N.

Read integers A and B from input file and write their sum in output file.

The Fibonacci sequence of numbers is known: F1 = 1; F2 = 1; Fn+1 = Fn + Fn-1, for n>1. You have to find S - the sum of the first K Fibonacci numbers.

There is sequence 1, 12, 123, 1234, …, 12345678910, … . Given first N elements of that sequence. You must determine amount of numbers in it that are divisible b...

You are given natural numbers a and b. Find a^b-b^a.

Once upon a time Professor Idioticideasinventor was travelling by train. Watching cheerless landscape outside the window, he decided to invent the theme of his ...

In the English language, nouns are inflected by grammatical number - that is singular or plural. In this problem we use a simple model of constructing plural fr...