There are $n$ children and $m$ apples that will be distributed to them. Your task is to count the number of ways this can be done.
For example, if $n=3$ and $m=2$ , there are $6$ ways: $[0,0,2]$ , $[0,1,1]$ , $[0,2,0]$ , $[1,0,1]$ , $[1,1,0]$ and $[2,0,0]$ .
The only input line has two integers $n$ and $m$ .
Print the number of ways modulo $10^9+7$ .