#include <bits/stdc++.h>
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
#define int long long
#define ff first
#define ss second
#define pb push_back
#define y1 zildjian
#define left radio
#define right head
using namespace std;
const int N = 2501;
const int INF = 1e18;
const int mod = 1e9+7;
const int mod1 = 998244353;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
int n,m;
int a[N][N];
void solve(){
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-'0';
}
}
int mn1 = m;
for(int i = 1;i<=n;i++){
int lst = 0;
for(int j = 1;j<=m;j++){
if(a[i][j] == 0){
if(lst+1 != j){
mn1 = min(mn1,j-lst-1);
}
lst = j;
}
}
if(lst+1 != m+1){
mn1 = min(mn1,(m+1)-lst-1);
}
}
int mn2 = n;
for(int j = 1;j<=m;j++){
int lst = 0;
for(int i = 1;i<=n;i++){
if(a[i][j] == 0){
if(lst+1 != i){
// cout<<lst<<' '<<i<<' '<<j<<'\n';
mn2 = min(mn2,i-lst-1);
}
lst = i;
}
}
if(lst+1 != n+1){
mn2 = min(mn2,(n+1)-lst-1);
}
}
cout<<mn1*mn2<<'\n';
}
signed main(){
// freopen("bootfall.in","r",stdin);
// freopen("bootfall.out","w",stdout);
ios_base::sync_with_stdio(0);
cin.tie(nullptr);
// cout.tie(nullptr);
int t = 1;
// cin>>t;
for(int i = 1;i<=t;i++){
// cout<<"Case "<<i<<": ";
solve();
}
}
