# Largest Rectangle

Given a matrix (`H` × `W`) which contains only 1 and 0, find the area of the largest rectangle which only contains 0s.

## Input

`H` `W`
`c`_{1,1} `c`_{1,2} ... `c`_{1,W}
`c`_{2,1} `c`_{2,2} ... `c`_{2,W}
:
`c`_{H,1} `c`_{H,2} ... `c`_{H,W}

In the first line, two integers `H` and `W` separated by a space character are given. In the following `H` lines, `c`_{i,j}, elements of the `H` × `W` matrix, are given.

## Output

Print the area (the number of 0s) of the largest rectangle.

## Constraints

## Sample Input

4 5
0 0 1 0 0
1 0 0 0 0
0 0 0 1 0
0 0 0 1 0

## Sample Output

6