#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 2512;
int s[N][N];
int next_one[N][N], prev_one[N][N], up[N][N], down[N][N];
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n, m;
cin >> n >> m;
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++) {
char c;
cin >> c;
s[i][j] = c - '0';
}
for (int i = 1; i <= n; i++) {
for (int j = m; j >= 1; --j) if (s[i][j])
next_one[i][j] = (s[i][j + 1] ? next_one[i][j + 1] : j + 1);
for (int j = 1; j <= m; j++) if (s[i][j])
prev_one[i][j] = (s[i][j - 1] ? prev_one[i][j - 1] : j - 1);
}
for (int j = 1; j <= m; j++) {
for (int i = 1; i <= n; i++) if (s[i][j])
up[i][j] = (s[i - 1][j] ? up[i - 1][j] : i - 1);
for (int i = n; i >= 1; --i) if (s[i][j])
down[i][j] = (s[i + 1][j] ? down[i + 1][j] : i + 1);
}
int inf = 1e9;
int best_width = inf, best_height = inf;
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++) if (s[i][j]) {
best_height = min(best_height, down[i][j] - up[i][j] - 1);
best_width = min(best_width, next_one[i][j] - prev_one[i][j] - 1);
}
assert(best_width < inf && best_height < inf);
cout << best_width * best_height << "\n";
}
