//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx,avx2,fma")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ordered_set tree <pair <int, int>, null_type, less <pair <int, int> >, rb_tree_tag, tree_order_statistics_node_update>
using namespace __gnu_pbds;
#define ll long long
#define db double
#define pb push_back
#define ppb pop_back
#define fi first
#define se second
#define mp make_pair
#define size(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define endl "\n"
//#define int long long
using namespace std;
void dout() {
cerr << endl;
}
template <typename Head, typename... Tail>
void dout(Head H, Tail... T) {
cerr << H << ' ';
dout(T...);
}
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
typedef pair <int, int> pii;
const int N = 2503, inf = 1e4;
int n, m, a[N][N], H = inf, W = inf;
int row[N], col[N];
void solve(int tc) {
// check for (int i = 0; i < n; j++)
cin >> n >> m;
char c;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> c;
a[i][j] = (c - '0');
}
}
int cur;
for (int i = 1; i <= n; i++) {
cur = 0;
memset(row, 0, sizeof(row));
for (int j = 1; j <= m; j++) {
if (a[i][j]) {
row[j] = row[j - 1] + 1;
cur++;
} else if (cur > 0) {
W = min(W, cur);
cur = 0;
}
}
}
for (int j = 1; j <= m; j++) {
cur = 0;
memset(col, 0, sizeof(col));
for (int i = 1; i <= n; i++) {
if (a[i][j]) {
col[i] = col[i - 1] + 1;
cur++;
} else if (cur > 0) {
H = min(H, cur);
cur = 0;
}
}
}
cout << H * W;
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
int tc = 1;
// cin >> tc;
for (int i = 0; i < tc; i++) {
solve(i);
// cleanup();
}
}
