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

Constraints

* 1 ≤ H, W ≤ 1,400

Input


H W
c1,1 c1,2 ... c1,W
c2,1 c2,2 ... c2,W
:
cH,1 cH,2 ... cH,W


In the first line, two integers H and W separated by a space character are given. In the following H lines, ci,j, elements of the H × W matrix, are given.

Output

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

Example

Input

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


Output

6
import sys
# import re
import math
import collections
# import decimal
import bisect
import itertools
import fractions
# import functools
import copy
# import heapq
import decimal
# import statistics
import queue

# import numpy as np

sys.setrecursionlimit(10000001)
INF = 10 ** 16
MOD = 10 ** 9 + 7
# MOD = 998244353

ni = lambda: int(sys.stdin.readline())
ns = lambda: map(int, sys.stdin.readline().split())
na = lambda: list(map(int, sys.stdin.readline().split()))


# ===CODE===

def largestRectangInHistgram(heights):
    stack = [-1]
    maxArea = 0

    for i in range(len(heights)):
        # we are saving indexes in stack that is why we comparing last element in stack
        # with current height to check if last element in stack not bigger then
        # current element
        while stack[-1] != -1 and heights[stack[-1]] > heights[i]:
            lastElementIndex = stack.pop()
            maxArea = max(maxArea, heights[lastElementIndex] * (i - stack[-1] - 1))
        stack.append(i)

    # we went through all elements of heights array
    # let's check if we have something left in stack
    while stack[-1] != -1:
        lastElementIndex = stack.pop()
        maxArea = max(maxArea, heights[lastElementIndex] * (len(heights) - stack[-1] - 1))

    return maxArea


def main():
    h, w = ns()
    mat = [na() for _ in range(h)]

    current = [0 for _ in range(w + 1)]

    ans = 0
    for i in range(h):
        for j in range(w):
            current[j] = current[j] + (mat[i][j] ^ 1) if mat[i][j]==0 else 0
        # current = [0] + current + [0]
        ans = max(ans, largestRectangInHistgram(current))

    print(ans)


if __name__ == '__main__':
    main()

