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;
  vector<vector<int>> map;
  for (int i = 0; i < H; i++) {
    vector<int> line;
    for (int j = 0; j < W; j++) {
      int state;
      cin >> state;
      line.push_back(state == 0 ? 1 : 0);
    }
    map.push_back(line);
  }
  for (int i = 0; i < H - 1; i++) {
    for (int j = 0; j < W; j++) {
      if (map[i + 1][j] != 0) {
        map[i + 1][j] += map[i][j];
      }
    }
  }
  int maxValue = 0;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      int minHight = map[i][j];
      for (int k = j;; k++) {
        if (k >= W || map[i][k] == 0) {
          int buf = k - j + 1 * minHight;
          maxValue = maxValue > buf ? maxValue : buf;
          break;
        }
        minHight = minHight < map[i][j] ? minHight : map[i][j];
      }
    }
  }
  cout << maxValue << endl;
}
