#include <bits/stdc++.h>
using namespace std;
const int MAXN = 2501;
//int dp[MAXN][MAXN];
char a[MAXN][MAXN];
//int sum[MAXN][MAXN];
signed main() {
int n, m;
cin >> n >> m;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> a[i][j];
//sum[i][j] = sum[i-1][j]+sum[i][j-1]-sum[i-1][j-1]+int(a[i][j] == '1');
}
}
//for (int i = 1; i <= n; i++) {
// for (int j = 1; j <= n; j++) {
// for (int a = 1; a <= i; a++) {
// for (int b = 1; b <= j; b++) {
// if (get(a, b, i, j))
// dp[i - a + 1][j - b + 1] = 1;
// }
// }
// }
//}
int mnj = INT_MAX, mni = INT_MAX;
for (int i = 1; i <= n; i++) {
for (int l = 1; l <= m;) {
int r = l, cnt = 0;
while (r <= m && a[i][r] == '1') r++, cnt++;
l = r + 1;
if (cnt)
mnj = min(mnj, cnt);
}
}
for (int j = 1; j <= m; j++) {
for (int l = 1; l <= n;) {
int r = l, cnt = 0;
while (r <= n && a[r][j] == '1') r++, cnt++;
l = r + 1;
if (cnt)
mni = min(mni, cnt);
}
}
if (mni == INT_MAX) cout << 0;
else cout << mni * mnj << '\n';
return 0;
}
