#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int MAXN = 55;
ll dp[MAXN][MAXN][MAXN][MAXN];
int a[MAXN][MAXN];
ll rec(int ar, int ac, int br, int bc) {
if(ar > br || ac > bc) return 0;
if(ar == br && ac == bc) return 0;
if(dp[ar][ac][br][bc] != -1) return dp[ar][ac][br][bc];
ll res = LLONG_MAX;
for(int i = ar;i < br;i++) { // row cut
res = min(res, rec(ar, ac, i, bc) + rec(i + 1, ac, br, bc));
}
for(int i = ac; i < bc;i++) {
res = min(res, rec(ar, ac, br, i) + rec(ar, i + 1, br, bc));
}
for(int i =ar;i <= br;i++) {
for(int j = ac; j <= bc;j++) {
res += a[i][j];
}
}
return dp[ar][ac][br][bc] = res;
}
int main() {
memset(dp, -1, sizeof(dp));
int n, m;
cin >> n >> m;
for(int i =0;i < n;i++) {
for(int j =0; j < m;j++) {
cin >> a[i][j];
}
}
cout << rec(0, 0, n - 1, m -1) << '\n';
}
