#826. Combinations C(n, k)
You get n and k. Find C(n, k) with the recursive formula C(n,k) = C(n-1,k-1) + C(n-1,k) (remember the answers you already found).
### Input
n k (0 ≤ k ≤ n ≤ 30).
### Output
Answer.
Examples
Input
10 5
Output
252
Input
16 12
Output
1820
💡 You can solve it with Python, JavaScript or blocks. Read the input line by line with input(). Don't print a question (like input("Number: ")). Print exactly what the output asks for, nothing more.