#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define fi first
#define se second
const ll N = 2600;
ll n,m;
char a[N][N];
ll mins,temp,mins1;
int main() {
cin >> n >> m;
for(int i=1; i<=n; i++) {
for(int j=1; j<=m; j++) {
cin >> a[i][j];
}
}
mins = 1e9;
mins1 = 1e9;
for(int i=1; i<=n; i++) {
temp = 0;
if(a[i][1] == '1') temp++;
for(int j=2; j<=m; j++) {
if(a[i][j] == a[i][j-1] && a[i][j] == '1') {
temp++;
}
else {
// cout << "i " << i << " " << temp << endl;
if(temp != 0)mins = min(mins,temp);
if(a[i][j] == '0') temp = 0;
else temp = 1;
}
}
}
if(temp != 0)mins = min(mins,temp);
// cout << "temp " << mins << endl;
temp = 0;
for(int i=1; i<=m; i++) {
temp = 0;
if(a[1][i] == '1') temp++;
for(int j=2; j<=n; j++) {
if(a[j][i] == a[j-1][i] && a[j][i] == '1') {
temp++;
}
else {
// cout << "i " << i << " " << temp << endl;
if(temp != 0)mins1 = min(mins1,temp);
if(a[j][i] == '0') temp = 0;
else temp = 1;
}
}
}
if(temp != 0)mins1 = min(mins1,temp);
// cout << mins << " " << mins1 << endl;
cout << mins * mins1 << endl;
}
/*
10 1
0
0
0
1
1
0
0
1
1
1
9 1
011111011
5 6
001000
111110
111110
011110
000100
*/
