Practice 2D array with the exercise "Largest Binary Rectangle"

Learning Opportunities

This puzzle can be solved using the following concepts. Practice using these concepts and improve your skills.

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

Output

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