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>
const double PI = 3.14159265358979323846;
const double esp = 1e-9;
const int infi = (int)1e+9 + 10;
const long long infll = (long long)1e+17 + 10;
int h, w;
int map[1401][1401];
int main() {
  std::cin >> h >> w;
  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      std::cin >> map[i][j];
      map[i][j] = (1 - map[i][j]);
    }
  }
  for (int i = 0; i < h; ++i) {
    for (int j = w - 2; j >= 0; --j) {
      if (map[i][j]) map[i][j] += map[i][j + 1];
    }
  }
  int ans = 0;
  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      int minEdge = infi;
      for (int k = i; k < h; ++k) {
        if (map[k][j] == 0) break;
        minEdge = std::min(minEdge, map[k][j]);
        ans = std::max(ans, (k - i + 1) * minEdge);
      }
    }
  }
  std::cout << ans << std::endl;
  return 0;
}
