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 x[2000][2000];
int H, W;
int main() {
  cin >> H >> W;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      cin >> x[i][j];
    }
    for (int j = 1; j < W; j++) {
      if (x[i][j] == 1) {
        x[i][j] = 0;
      } else {
        x[i][j] = x[i][j - 1] + 1;
      }
    }
  }
  int maxn = 0;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      int X = x[i][j], cnt = 0;
      for (int k = j; k >= 0; k--) {
        if (x[i][k] >= X) {
          cnt++;
        } else {
          break;
        }
      }
      maxn = max(maxn, cnt * X);
    }
  }
  cout << maxn << endl;
  return 0;
}
