#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int N, M;
cin >> N >> M;
vector<vector<int>> A(N, vector<int>(M));
for (int i = 0; i < N; i++) {
for (int j = 0; j < M; j++) {
char c;
cin >> c;
A[i][j] = c - '0';
}
}
const auto Solve = [&](const vector<vector<int>> &A) {
vector<vector<int>> H, V;
H.assign(N, vector<int>(M, 0));
V.assign(N, vector<int>(M, 0));
for (int i = 0; i < N; i++) {
for (int j = 0; j < M; j++) if (A[i][j] == 1) {
int jj = j;
while (jj + 1 < M && A[i][jj + 1] == 1) jj += 1;
for (int k = j; k <= jj; k++) {
H[i][k] = jj - j + 1;
}
j = jj;
}
}
for (int j = 0; j < M; j++) {
for (int i = 0; i < N; i++) if (A[i][j] == 1) {
int ii = i;
while (ii + 1 < N && A[ii + 1][j] == 1) ii += 1;
for (int k = i; k <= ii; k++) {
V[k][j] = ii - i + 1;
}
i = ii;
}
}
return pair(H, V);
};
auto [H, V] = Solve(A);
int ansN = N;
int ansM = M;
for (int i = 0; i < N; i++) {
for (int j = 0; j < M; j++) if (A[i][j] != 0) {
ansN = min(ansN, V[i][j]);
ansM = min(ansM, H[i][j]);
}
}
cout << ansN * ansM << '\n';
return 0;
}
