Hearthstone II

Time Limit: 2000 ms Memory Limit: 65536 KiB

Problem Description

The new season has begun, you have n competitions and m well prepared decks during the new season. Each competition you could use any deck you want, but each of the decks must be used at least once. Now you wonder how many ways are there to plan the season — to decide for each competition which deck you are going to used. The number can be very huge, mod it with 10^9 + 7.
 

Input

The input file contains several test cases, one line for each case contains two integer numbers n and m (1 ≤ m ≤ n ≤ 100).
 

Output

One line for each case, output one number — the number of ways.

Sample Input

3 2
100 25

Sample Output

6
354076161

Hint

 

Source

2014年山东省第五届ACM大学生程序设计竞赛