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;
const int N = 1403;
int n, m;
int c[N][N];
int lf[N][N], up[N][N];
int mx = 0;
int main() {
  cin >> n >> m;
  for (int i = 0; i < n; ++i)
    for (int j = 0; j < m; ++j) cin >> c[i][j];
  memset(lf, 0, sizeof lf);
  memset(up, 0, sizeof up);
  for (int i = 0; i < n; ++i)
    for (int j = 0; j < m; ++j)
      if (!c[i][j]) {
        if (j) lf[i][j] = lf[i][j - 1] + 1;
        if (i) up[i][j] = up[i - 1][j] + 1;
        if (i && j) {
          lf[i][j] = max(lf[i][j], lf[i - 1][j - 1] + 1);
          up[i][j] = max(up[i][j], up[i - 1][j - 1] + 1);
        }
        mx = max(mx, lf[i][j] * up[i][j]);
      }
  cout << mx << endl;
  return 0;
}
