#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define endl '\n';
#define el cout<<endl
#define fr(i,n,m) for(int i=n;i<=m;i++)
#define frr(i,n,m) for(int i=n;i>=m;i--)
#define vi vector<int>
#define pi pair<int,int>
#define vpi vector<pi>
#define inf 1e18
int n, m, k, l, r, num = 0, ans = 0, sum = 0, mi = inf, ma = 0;
int a, b, c, d, e, x, y, z, w, q;
const int N = 2500 + 5;
// vpi adj[N];
string v[N];
void solve() {
cin >> n >> m;
fr(i, 0, n - 1) {
cin >> v[i];
}
mi = inf;
fr(i, 0, n - 1) {
a = 0;
fr(j, 0, m - 1) {
if (v[i][j] == '1') {
a++;
}
else {
if (a) {
mi = min(mi, a); a = 0;
}
}
}
if (a) mi = min(mi, a);
}
ma = inf;
fr(j, 0, m - 1) {
a = 0;
fr(i, 0, n - 1) {
if (v[i][j] == '1') {
a++;
}
else {
if (a) {
ma = min(ma, a); a = 0;
}
}
}
if (a) ma = min(ma, a);
}
if(mi==inf or ma==inf) cout<< n * m;
else cout << mi * ma;
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int T = 1;
// cin >> T;
while (T--) {
cout << fixed << setprecision(12); solve();
el;
} return 0;
}
