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Background

Description

给定两个非负整数n和m（1<=n<=m<=15），编写函数计算组合数C(n, m)

Format

Input

第一行输入n（1<=n<=15）

第二行输入m（1<=m<=15）

Output

输出组合数C(n, m)的结果值

Samples

5
2

10

15
5

3003

Limitation

1s, 1024KiB for each test case.