Jumping stones
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## Algorithms, Dynamic Programming, Introduction to Dynamic Programming 1

Problem
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There are $n$ stones in a row from left to right. You are standing on the first stone. From every step from stone number $i$, you can jump at most $k$ stones further ($i + 1,\ i + 2,\ \dots,\ i + k$). You cannot jump over stone number $n$. How many ways are there to travel to stone number $n$?

Input format

First line: $n$ and $k$

Output format

Print the answer modulo $10^9+7$.

SAMPLE INPUT
5 2


SAMPLE OUTPUT
5

Explanation

-

Time Limit: 1.0 sec(s) for each input file.
Memory Limit: 256 MB
Source Limit: 1024 KB

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