#include <bits/stdc++.h>
int N, M;
int a[2505][2505];
int width, height;
int main() {
std::cin.tie(0)->sync_with_stdio(0);
std::cin >> N >> M;
for (int i = 1; i <= N; ++i) {
std::string s; std::cin >> s;
for (int j = 1; j <= M; ++j) {
a[i][j] = (s[j - 1] == '1');
}
}
width = M + 1, height = N + 1;
for (int i = 1; i <= N; ++i) {
for (int j = 1, cnt = 0; j <= M + 1; ++j) {
if (a[i][j] == 1) {
cnt++;
} else {
if (a[i][j - 1] == 1) width = std::min(width, cnt);
cnt = 0;
}
}
}
for (int j = 1; j <= M; ++j) {
for (int i = 1, cnt = 0; i <= N + 1; ++i) {
if (a[i][j] == 1) {
cnt++;
} else {
if (a[i - 1][j] == 1) height = std::min(height, cnt);
cnt = 0;
}
}
}
if (height == N + 1) height = 0;
std::cout << width * height << '\n';
return 0;
}
