Solve the programming task below in a Python markdown code block.
You are given two integers $N$ and ${L}}$. Compute the number of unrooted labelled trees with exactly $N$ nodes and exactly ${L}$ leafs. This number can be huge, so please output it's modulo $10^9+7$.

Input Format

The first line of input consists of two space separated integers $N$ and ${L}$.

Constraints

$1\leq L<N\leq10^{6}$

Output Format

Display an answer to the problem on first line of the output.

Sample Input
5 2
Sample Output

60