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
#!python3

from collections import deque

iim = lambda: map(int, input().rstrip().split())

def calc(dp):
    ans = 0
    dq = deque([[0, 0]])
    #print(dp)
    for i, hi in enumerate(dp):
        j = i
        while dq[-1][1] > hi:
            j, h1 = dq.pop()
            ans = max(ans, (i - j) * h1)

        if dq[-1][1] < hi:
            dq.append([j, hi])

    i = len(dp)
    for j, hi in dq:
        ans = max(ans, (i - j) * hi)
    #print(i, dq, ans)
    return ans

def resolve():
    H, W = iim()

    dp = [0] * W
    dp0 = dp[:]
    ans = 0
    for i in range(H):
        C = list(iim())

        for i, ci in enumerate(C):
            dp[i] = 0 if ci else dp0[i] + 1

        ans = max(ans, calc(dp))
        dp, dp0 = dp0, dp

    print(ans)

if __name__ == "__main__":
    resolve()

