#include <bits/stdc++.h>
using namespace std;
using ll = long long;
// using ld = long double;
#define all(x) begin(x), end(x)
#ifdef LOCAL
#define debug(...) __VA_ARGS__;
#else
#define debug(...)
#endif
template<class A, class B> ostream& operator<<(ostream& os, const pair<A, B> &p);
template<class T> ostream& operator<<(ostream& os, const vector<T> &v);
template<class T, size_t N> ostream& operator<<(ostream& os, const array<T, N> &v);
template<class A, class B>
ostream& operator<<(ostream& os, const pair<A, B> &p) {
return os << '(' << p.first << ',' << p.second << ')';
}
template<class T>
ostream& operator<<(ostream& os, const vector<T> &v) {
os << '{'; bool fs = 1;
for(auto &i : v) { if(!fs) os << ','; os << i; fs = 0; }
return os << '}';
}
template<class T, size_t N>
ostream& operator<<(ostream& os, const array<T, N> &v) {
os << '{'; bool fs = 1;
for(auto &i : v) { if(!fs) os << ','; os << i; fs = 0; }
return os << '}';
}
void init() {
}
void solve(int tt = 0) {
int n, m; cin >> n >> m;
vector a(n, vector<int>(m));
bool ok = 0;
for(auto &v : a) for(int &i : v) {
char c; cin >> c;
i = c - '0';
ok |= i;
}
if(!ok) return void(cout << 0 << '\n');
const int INF = 1e9;
int h = INF, w = INF;
{
for(int i = 0; i < n; i++) {
int cur = 0;
for(int j = 0; j < m; j++) {
if(a[i][j] == 0) {
if(cur != 0) w = min(w, cur);
cur = 0;
} else {
cur++;
}
}
if(cur != 0) w = min(w, cur);
}
}
{
for(int j = 0; j < m; j++) {
int cur = 0;
for(int i = 0; i < n; i++) {
if(a[i][j] == 0) {
if(cur != 0) h = min(h, cur);
cur = 0;
} else {
cur++;
}
}
if(cur != 0) h = min(h, cur);
}
}
debug(cerr << h << ' ' << w << '\n');
if(h != INF && w != INF) cout << (ll)h * w << '\n';
else cout << 0 << '\n';
}
void reset() {
}
int main() {
ios::sync_with_stdio(0); cin.tie(0);
int t = 1; // cin >> t;
init();
for(int i = 1; i <= t; i++) solve(i), reset();
return 0;
}
