#pragma GCC optimize("O3")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,tune=native")
//#pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
const int N = 2501;
char a[N][N];
int main() {
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int n, m;
cin >> n >> m;
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
cin >> a[i][j];
}
}
int h = n, w = m;
for (int i = 0; i < n; i++) {
int kek = 0;
for (int j = 0; j < m; j++) {
if (a[i][j] == '1') {
kek++;
} else {
if (kek) {
w = min(kek, w);
}
kek = 0;
}
}
if (kek) {
w = min(kek, w);
}
}
for (int j = 0; j < m; j++) {
int kek = 0;
for (int i = 0; i < n; i++) {
if (a[i][j] == '1') {
kek++;
} else {
if (kek) {
h = min(kek, h);
}
kek = 0;
}
}
if (kek) {
h = min(kek, h);
}
}
cout << h * w;
return 0;
}
