#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define sp <<" "<<
#define endl "\n"
int dp[50][50][50][50];
vector<vector<int>> grid, pref;
int query(int lr, int rr, int lc, int rc) {
return { 0
+ pref[rr][rc]
- (lr > 0 ? pref[lr-1][rc] : 0)
- (lc > 0 ? pref[rr][lc-1] : 0)
+ (lr > 0 and lc > 0 ? pref[lr-1][lc-1] : 0)
};
}
int decomp(int lr, int rr, int lc, int rc) {
int sz = (rr - lr + 1) * (rc - lc + 1);
if (sz == 1) return 0;
if (dp[lr][rr][lc][rc] != -1) return dp[lr][rr][lc][rc];
int mn = INT_MAX;
for (int i = lr; i < rr; i++) {
mn = min(mn, decomp(lr, i, lc, rc) + decomp(i+1, rr, lc, rc));
}
for (int i = lc; i < rc; i++) {
mn = min(mn, decomp(lr, rr, lc, i) + decomp(lr, rr, i+1, rc));
}
return dp[lr][rr][lc][rc] = mn + query(lr, rr, lc, rc);
}
void solve() {
int n, m; cin >> n >> m;
grid.resize(n);
for (int i = 0; i < n; i++) grid[i].resize(m);
int sum = 0;
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
cin >> grid[i][j];
sum += grid[i][j];
}
}
pref = grid;
for (int i = 1; i < n; i++) pref[i][0] += pref[i-1][0];
for (int i = 1; i < m; i++) pref[0][i] += pref[0][i-1];
for (int i = 1; i < n; i++) {
for (int j = 1; j < m; j++) {
pref[i][j] += pref[i-1][j] + pref[i][j-1] - pref[i-1][j-1];
}
}
for (int i = 0; i < 50; i++) {
for (int j = 0; j < 50; j++) {
for (int k = 0; k < 50; k++) {
for (int l = 0; l < 50; l++) {
dp[i][j][k][l] = -1;
}
}
}
}
cout << decomp(0, n-1, 0, m-1) << endl;
}
signed main() {
cin.tie(0);
ios_base::sync_with_stdio(false);
int t = 1;
// cin >> t;
while (t--)
solve();
}
