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
#include <bits/stdc++.h>
int A[1400][1400];
int m[1400][1400];
int main() {
  int i, j, k, x, y, r, M = 0, t = 0, z;
  scanf("%d%d", &y, &x);
  for (j = 0; j < y; j++)
    for (i = 0; i < x; i++) scanf("%d", A[j] + i);
  for (j = 0; j < y; j++)
    for (r = i = 0; i < x; m[j][i] = r, i++) r = A[j][i] == 0 ? r + 1 : 0;
  for (r = i = 0; i < x; i++)
    for (j = 0; j < y; j++)
      for (M = x, k = j; k < y; k++) {
        if (M > m[k][i]) M = m[k][i];
        int z = k - j + 1;
        if (r < M * z) r = M * z;
      }
  printf("%d\n", r);
  return 0;
}
