A community lottery forms a committee by choosing a group of members from a pool of applicants. Given the pool size n and the committee size r, count how many distinct committees of exactly r members can be formed. The order in which members are picked does not matter, and no member may appear twice. Because the count can be enormous, report it modulo 1000000007.
Input format
A single line with two integers n and r.
Output format
A single integer: the number of distinct committees, modulo 1000000007.
Constraints
- 0 <= r <= n <= 2000