Grasshopper

One of the teachers has a grasshopper living in their room, and it loves to jump on a one-dimensional checkered board of length $n$ cells. Unfortunately for the grasshopper, it can only jump forward by $1,2,\dots ,k$ cells.

One day, the teachers became curious about how many ways the grasshopper could jump from the first cell to the last. Help them answer this question.

Input

Two integers $n$ and $k(1\le n\le 30,1\le k\le 10)$.

Output

Print the number of ways the grasshopper can jump from the first cell to the last.

Examples