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 mp[1401][1401];
int h, w;
struct dat {
  int h, i;
};
int calc(int A[]) {
  stack<dat> S;
  int res = 0;
  for (int i = 0; i <= w; i++) {
    int h = A[i];
    if (S.empty() || S.top().h < h)
      S.push((dat){h, i});
    else if (S.top().h == h)
      ;
    else {
      int ni = i;
      while (!S.empty() && S.top().h > h) {
        dat t = S.top();
        S.pop();
        ni = t.i;
        int area = (i - t.i + 1) * h;
        res = max(res, area);
      }
      S.push((dat){h, ni});
    }
  }
  return res;
}
int main() {
  cin >> h >> w;
  for (int i = 0; i < h; i++)
    for (int j = 0; j < w; j++) cin >> mp[i][j], mp[i][j] = !mp[i][j];
  for (int j = 0; j < w; j++)
    for (int i = 1; i < h; i++)
      if (mp[i][j]) mp[i][j] = mp[i - 1][j] + 1;
  int ans = 0;
  for (int i = 0; i < h; i++) ans = max(ans, calc(mp[i]));
  cout << ans << endl;
  return 0;
}
