#include <bits/stdc++.h>
using i64 = long long;
#ifdef DEBUG
#include "/home/ahmetalp/Desktop/Workplace/debug.h"
#else
#define debug(...) void(23)
#endif
int main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
int N, M;
std::cin >> N >> M;
std::vector<std::string> A(N);
for (int i = 0; i < N; ++i) {
std::cin >> A[i];
}
int x = M, y = N;
for (int r = 0; r < N; ++r) {
for (int i = 0, j = 0; i < M; i = j) {
if (A[r][i] == '0') {
j++;
} else {
while (j < M && A[r][j] == '1') {
j++;
}
x = std::min(x, j - i);
}
}
}
for (int c = 0; c < M; ++c) {
for (int i = 0, j = 0; i < N; i = j) {
if (A[i][c] == '0') {
j++;
} else {
while (j < N && A[j][c] == '1') {
j++;
}
y = std::min(y, j - i);
}
}
}
assert(x != 0 && y != 0);
std::cout << x * y << '\n';
return 0;
}
