小Q非常喜欢数学，但是他的口算能力非常弱。因此他找到了小T，给了小T一个长度为n的正整数序列a1,a2,…,an，要求小T抛出m个问题以训练他的口算能力。...

You are given two positive integers aa and bb.

You are given the array aa consisting of nn elements and the integer k≤nk≤n.

The organizers of a programming contest have decided to present t-shirts to participants. There are six different t-shirts sizes in this problem: S, M, L, XL, X...

You have array of nn numbers a1,a2,…,ana1,a2,…,an.

You have integer nn. Calculate how many ways are there to fully cover belt-like area of 4n−24n−2 triangles with diamond shapes.

You have unweighted tree of nn vertices. You have to assign a positive weight to each edge so that the following condition would hold:

Today, Mezo is playing a game. Zoma, a character in that game, is initially at position x=0x=0. Mezo starts sending nn commands to Zoma. There are two possible ...

The task is simple: given any positive integer N, you are supposed to count the total number of 1's in the decimal form of the integers from 1 to N. For example...

Polycarp has three sisters: Alice, Barbara, and Cerene. They're collecting coins. Currently, Alice has aa coins, Barbara has bb coins and Cerene has cc coins. R...