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;
  cin >> h >> w;
  int maxlen[1401][1401] = {};
  for (int i = 1; i <= h; i++) {
    for (int j = 1; j <= w; j++) {
      int c;
      cin >> c;
      if (c == 1) continue;
      maxlen[i][j] = maxlen[i - 1][j] + 1;
    }
  }
  int ans = 0;
  for (int i = 1; i <= h; i++) {
    stack<pair<int, int> > st;
    for (int j = 1; j <= w; j++) {
      if (st.empty() || (st.top()).first < maxlen[i][j]) {
        st.push(make_pair(maxlen[i][j], j));
      } else if ((st.top()).first > maxlen[i][j]) {
        while (!st.empty()) {
          if ((st.top()).first < maxlen[i][j]) {
            st.push(make_pair(maxlen[i][j], j));
            break;
          } else {
            ans = max(ans, (st.top()).first * (j - (st.top()).second));
            st.pop();
          }
        }
      }
    }
  }
  cout << ans << endl;
  return 0;
}
