#include <bits/stdc++.h>
using namespace std;
#define int long long int
int n, m, r[55][55], pref[55][55], dp[55][55][55][55];
void find(int i1, int j1, int i2, int j2) {
if (dp[i1][j1][i2][j2] != -1) {
return;
}
dp[i1][j1][i2][j2] = INT_MAX;
int v = pref[i2][j2]-pref[i1-1][j2]-pref[i2][j1-1]+pref[i1-1][j1-1];
for (int i = i1; i < i2; i++) {
find(i1, j1, i, j2);
find(i+1, j1, i2, j2);
dp[i1][j1][i2][j2] = min(dp[i1][j1][i2][j2], dp[i1][j1][i][j2]+dp[i+1][j1][i2][j2]+v);
}
for (int j = j1; j < j2; j++) {
find(i1, j1, i2, j);
find(i1, j+1, i2, j2);
dp[i1][j1][i2][j2] = min(dp[i1][j1][i2][j2], dp[i1][j1][i2][j]+dp[i1][j+1][i2][j2]+v);
}
}
void solve() {
cin >> n >> m;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
for (int x = 1; x <= m; x++) {
for (int y = 1; y <= m; y++) {
dp[i][x][j][y] = -1;
}
}
}
}
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> r[i][j];
dp[i][j][i][j] = 0;
}
}
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]+r[i][j];
}
}
find(1, 1, n, m);
cout << dp[1][1][n][m] << endl;
}
int32_t main() {
ios::sync_with_stdio(0);
cin.tie(0);
int t;
t = 1;
while(t--) {
solve();
}
}
