#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
void solve () {
int n, m; cin >> n >> m;
vector <vector <char>> a(n + 1, vector <char> (m + 1));
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> a[i][j];
}
}
int dx = n, dy = m;
for (int i = 1; i <= n; i++) {
int cnt = 0;
for (int j = 1; j <= m; j++) {
if (a[i][j] == '1') {
cnt++;
} else if (cnt > 0) {
dy = min(dy, cnt);
cnt = 0;
}
}
if (cnt > 0) {
dy = min(dy, cnt);
cnt = 0;
}
}
for (int j = 1; j <= m; j++) {
int cnt = 0;
for (int i = 1; i <= n; i++) {
if (a[i][j] == '1') {
cnt++;
} else if (cnt > 0) {
dx = min(dx, cnt);
cnt = 0;
}
}
if (cnt > 0) {
dx = min(dx, cnt);
cnt = 0;
}
}
cout << dx * dy << '\n';
}
signed main () {
ios::sync_with_stdio(0); cin.tie(0);
int tc = 1; //cin >> tc;
while (tc--) solve();
}
