## Goal

Given a `width` x `height` binary matrix filled with 0's and 1's, find the largest rectangle containing only 1's and return its area.
Input

**Line 1:** Two separated integers `width` and `height`

**Next** `height` **lines**: `width` separated integers (Either 1 or 0)

Output

An integer of the largest rectangle containing only 1's area

Output 0 if there is no rectangle that only contain 1's

Constraints

0 < `width`, `height` < 51

Example

Input

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