Ricky has N different balls and John has R different bags. Their teacher Ms.Samara wants them to distribute these N balls into R bags such that each bag gets at least one ball. Can you find the number of ways of doing so ?

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