Grasshopper lives in the teacher's room. It likes to jump on one dimensional checkerboard. The length of the board is n cells. To its regret, it can jump only on 1, 2, ..., k cells forward.

Once teachers wondered in how many ways a grasshopper can reach the last cell from the first one. Help them to answer this question.

Input

Two integers n and k (1 ≤ n ≤ 30, 1 ≤ k ≤ 10).

Output

Print the number of ways for grasshopper to leap from the first cell to the last.