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>
using namespace std;
int c[1401][1401] = {};
int a(int x1, int x2, int y1, int y2) {
  int b = c[x1][y1] + c[x2][y2] - c[x1][y2] - c[x2][y1];
  if (b != 0) b = 1;
  return b;
}
int main() {
  int h, w;
  cin >> h >> w;
  for (int i = 1; i <= h; i++) {
    for (int j = 1; j <= w; j++) {
      cin >> c[i][j];
      c[i][j] += c[i][j - 1] + c[i - 1][j] - c[i - 1][j - 1];
    }
  }
  int max = 0;
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      for (int k = i + 1; k <= h; k++) {
        for (int l = j + 1; l <= w; l++) {
          if (a(i, k, j, l) == 0) {
            if (max < (k - i) * (l - j)) max = (k - i) * (l - j);
          } else
            break;
        }
      }
    }
  }
  cout << max << endl;
}
