Simple Math
Problem
Find the number of ways of distributing N objects into R groups such that each group gets 1 or more objects.
Input:
The one and only line of input contains two numbers separated by a single space, which are N and R respectively.
Output:
The corresponding answer modulo 10000007 in a single line and if no answer exist then print "-1".
Constraints:
1 <= N <= 100
1 <= R <= 100
Time Limit: 1
Memory Limit: 256
Source Limit:
Explanation
Let the 2 groups be A and B respectively. Case 1: A gets 1 object and B gets 3 Case 2: A gets 2 objects and B gets 2 Case 3: A gets 3 objects and B gets 1
