Problem8585--DPL_3_B : Largest Rectangle

8585: DPL_3_B : Largest Rectangle

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Time Limit : 1.000 sec  Memory Limit : 256 MiB

Description

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

Input

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

1 ≤ H, W ≤ 1,400

Sample 1 Input

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

Sample 1 Output

6

HINT

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