#include <bits/stdc++.h>
using namespace std;
const int N = 1e3 + 3;
const int inf = 1e9 + 7;
int a[N][N];
pair < int, int > d[N][N];
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr); cout.tie(nullptr);
int n, m;
cin >> n >> m;
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
char c;
cin >> c;
a[i][j] = c - '0';
}
}
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
if(a[i][j] == 0) d[i][j] = {0, 0};
else d[i][j].first = d[i][j - 1].first + 1, d[i][j].second = d[i - 1][j].second + 1;
}
}
int ans1 = N, ans2 = N;
for(int i = 1; i <= n; i++){
int cnt = 0;
for(int j = m; j >= 1; j--){
if(cnt) cnt--;
if(d[i][j].first && !cnt) ans1 = min(ans1, d[i][j].first), cnt = d[i][j].first;
}
}
for(int j = 1; j <= m; j++){
int cnt = 0;
for(int i = n; i >= 1; i--){
if(cnt) cnt--;
if(d[i][j].second && !cnt) ans2 = min(ans2, d[i][j].second), cnt = d[i][j].second;
}
}
if(ans1 == N) ans1 = 0;
cout << ans1 * ans2;
}
