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 main() {
  int h, w, s, max = 0;
  cin >> h >> w;
  int a[1401][1401] = {};
  for (int i = 1; i <= h; i++) {
    for (int j = 1; j <= w; j++) {
      cin >> s;
      if (s == 0)
        a[i][j] = a[i][j - 1] + 1;
      else
        a[i][j] = 0;
    }
  }
  for (int i = 1; i <= w; i++) {
    for (int j = 1; j <= i; j++) {
      int d = 0;
      for (int k = 1; k <= h; k++) {
        if (a[k][i] >= j) {
          d = d + j;
          if (max < d) max = d;
        } else
          d = 0;
      }
    }
  }
  cout << max << endl;
}
