CSES - HIIT Open 2017 - Grid
• Time limit: 2.00 s
• Memory limit: 512 MB
You are given an $n \times m$ grid whose each square is either black or white.

Count the number of rectangles whose each corner square is black.

Input

The first input line contains two integer $n$ and $m$: the size of the grid.

Then, there are $n$ lines of length $m$ that describe the grid. Each line consists of characters 0 (white) and 1 (black).

Output

Print the number of rectangles whose each corner square is black.

Constraints
• $1 \le n,m \le 3000$
Example

Input:
3 4 0111 0011 0101

Output:
2