#include<bits/stdc++.h>
#define ll long long
#define f first
#define s second
#define pb push_back
using namespace std;
ll n,m;
int a[2505][2505];
int main(){
ios::sync_with_stdio(false);
cin >> n >> m;
for(int i=1; i<=n; i++){
for(int j=1; j<=m; j++){
char x;
cin >> x;
a[i][j] = (x == '1');
}
}
ll indx = 1000000;
for(int i=1; i<=n; i++){
ll las = 0;
for(int j=1; j<=m; j++){
if(a[i][j] == 0){
las = j;
continue;
}
if(a[i][j + 1] == 0){
indx = min(indx , j - las);
}
}
}
ll indy = 1000000;
for(int i=1; i<=m; i++){
ll las = 0;
for(int j=1; j<=n; j++){
if(a[j][i] == 0){
las = j;
continue;
}
if(a[j + 1][i] == 0){
indy = min(indy , j - las);
}
}
}
if(indx == indy && indx == 1000000){
cout << 0;
return 0;
}
cout << indx * indy << '\n';
return 0;
}
