#include <bits/stdc++.h>
using namespace std;
#define int long long
mt19937_64 RNG(chrono::steady_clock::now().time_since_epoch().count());
void Solve() {
int n, m;
cin >> n >> m;
int total = 0;
int a[n + 1][m + 1];
for(int i = 1; i <= n; i++) {
for(int j = 1; j <= m; j++) {
cin >> a[i][j];
total += a[i][j];
if(a[i][j] == 0) {
a[i][j] = -1;
}
}
}
int grid[n + 1][m + 1];
for(int i = 0; i <= n; i++) {
for(int j = 0; j <= m; j++) {
grid[i][j] = 0;
}
}
grid[1][1] = a[1][1];
for(int i = 2; i <= n; i++) {;
grid[i][1] = grid[i - 1][1] + a[i][1];
}
for(int i = 2; i <= m; i++) {
grid[1][i] = grid[1][i - 1] + a[1][i];
}
for(int i = 2; i <= n; i++) {
for(int j = 2; j <= m; j++) {
grid[i][j] = grid[i - 1][j] + grid[i][j - 1] - grid[i - 1][j - 1] + a[i][j];
}
}
/*for(int i = 1; i <= n; i++) {
for(int j = 1; j <= m; j++) {
cout << grid[i][j] << " ";
}
cout << "\n";
}*/
//cout << "total = " << total << "\n";
int ans = INT_MAX;
for(int left = 1; left <= n; left++) {
for(int right = left; right <= n; right++) {
int left_col = 0;
for(int column = 1; column <= m; column++) {
int sum = grid[right][column] - grid[left - 1][column] - grid[right][left_col] + grid[left - 1][left_col];
int possible = (right - left + 1) * (column - left_col);
int zeros = (possible - sum) / 2;
int ones = total - (possible - zeros);
ans = min(ans, zeros + ones);
if(sum < 0) {
left_col = column;
}
}
}
}
cout << ans << "\n";
}
int32_t main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int t = 1;
//cin >> t;
while(t--) {
Solve();
}
return 0;
}
