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 tag[505][505];
int dp[505][505];
int main() {
  int n, m;
  while (cin >> n >> m) {
    for (int i = 1; i <= n; i++) {
      for (int j = 1; j <= m; j++) {
        cin >> tag[i][j];
        if (!tag[i][j]) dp[i][j] = dp[i][j - 1] + 1;
      }
    }
    for (int i = 1; i <= n; i++) {
      for (int j = 1; j <= m; j++) {
      }
    }
    int k, maxs = 0, l, x;
    for (int i = 1; i <= n; i++) {
      for (int j = 1; j <= m; j++) {
        x = dp[i][j];
        k = i;
        l = 1;
        while (k > 0) {
          x = min(x, dp[k][j]);
          maxs = max(maxs, x * l);
          l++;
          k--;
        }
      }
    }
    cout << maxs << endl;
  }
}
