#include <algorithm>
#include <cassert>
#include <cstring>
#include <deque>
#include <ios>
#include <iostream>
#include <map>
#include <vector>
#define ll long long
#define ull unsigned ll
#define ld long double
#define ff first
#define ss second
#define ln "\n"
#define pll pair<ll, ll>
using namespace std;
void solve(){
ll n, m; cin >> n >> m;
vector<vector<ll>> a(n, vector<ll>(m));
for (ll i=0; i<n; i++) for (ll j=0; j<m; j++) {
char x; cin >> x;
a[i][j]=x-'0';
}
ll w=2e18, h=2e18;
for (ll i=0; i<n; i++){
ll cc=0;
for (ll j=0; j<m; j++){
if (a[i][j]==1){
cc++;
}else {
if (cc) h=min(h, cc);
cc=0;
}
}
if (cc) h=min(h, cc);
}
for (ll j=0; j<m; j++){
ll cc=0;
for (ll i=0; i<n; i++){
if (a[i][j]==1){
cc++;
}else {
if (cc) w=min(w, cc);
cc=0;
}
}
if (cc) w=min(w, cc);
}
cout << h*w << ln;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(nullptr);
ll t=1;
// cin >> t;
while (t--)solve();
}
