**Time limit:**1.00 s**Memory limit:**512 MB

Two bishops attack each other if they are on the same diagonal.

**Input**

The only input line has two integers $n$ and $k$: the board size and the number of bishops.

**Output**

Print one integer: the number of ways modulo $10^9+7$.

**Constraints**

- $1 \le n \le 500$

- $1 \le k \le n^2$

**Example**

Input:

`5 4`

Output:

`2728`