#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<ll,ll>
#define pii pair<int,int>
#define fs first
#define sc second
#define tlll tuple<ll,ll,ll>
const int mxn = 2500;
int n,m;
int arr[mxn][mxn];
int main(){
ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin>>n>>m;
for(int i = 1;i<=n;i++){
for(int j= 1;j<=m;j++){
char c;
cin>>c;
arr[i][j] = c-'0';
}
}
int row = n,col = m;
for(int i = 1;i<=n;i++){
int dp = 0;
for(int j = 1;j<=m;j++){
if(arr[i][j])dp++;
else col = min(col,(dp?dp:m)),dp = 0;
}
if(dp)col = min(col,dp);
}
for(int i = 1;i<=m;i++){
int dp = 0;
for(int j = 1;j<=n;j++){
if(arr[j][i])dp++;
else row = min(row,(dp?dp:n)),dp = 0;
}
if(dp)row = min(row,dp);
}
//cout<<row<<','<<col<<endl;
cout<<row*col;
}
