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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

### Tags

### Subtasks and Limits

Subtask | Score | #TC | Time | Memory | Scoring |
---|---|---|---|---|---|

1 | 100 | 25 | 1s | 32MB | Average |

2 | 0 | 0 | 1s | 32MB | Average |

### Judge Compile Command

g++-7 ans.cpp -o pascal -Wall -static -O2 -lm -m64 -s -w -std=gnu++17 -fmax-errors=512