### ** pascal**

Pascal's triangle has the property that every number in the triangle is the sum of the two numbers above it.

1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1

You are given two integers *R* and *C*. Your task is to find the *C*^{th} number on the *R*^{th} row.

## Input

On the first line read in two space-separated integers

*R* and

*C* (1 ≤

*C* ≤

*R* ≤ 25).

## Output

On the first and only line output the

*C*^{th} number on the

*R*^{th} row of Pascal's triangle.

## Sample Input 1

5 2

## Sample Output 1

4