#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
int a[51][51];
int dp[51][51][51][51];
int su[51][51];
int pref(int r1, int c1, int r2, int c2) {
return su[r2][c2] - su[r2][c1] - su[r1][c2] + su[r1][c1];
}
int calc(int r1, int c1, int r2, int c2) {
if(dp[r1][c1][r2][c2] != -1) return dp[r1][c1][r2][c2];
if(r1 == r2 - 1 && c1 == c2 - 1) return dp[r1][c1][r2][c2] = 0;
int ans = 999999999;
for(int r = r1 + 1; r < r2; r++) {
ans = min(ans, calc(r1, c1, r, c2) + calc(r, c1, r2, c2));
}
for(int c = c1 + 1; c < c2; c++) {
ans = min(ans, calc(r1, c1, r2, c) + calc(r1, c, r2, c2));
}
return dp[r1][c1][r2][c2] = ans + pref(r1, c1, r2, c2);
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int r, c;
cin >> r >> c;
for(int i = 0; i <= r; i++) {
for(int j = 0; j <= c; j++) {
su[i][j] = 0;
}
}
for(int i = 0; i < r; i++) {
for(int j = 0; j < c; j++) {
cin >> a[i][j];
su[i+1][j+1] = su[i+1][j] + su[i][j+1] - su[i][j] + a[i][j];
}
}
for(int i = 0; i <= r; i++) {
for(int j = i; j <= r; j++) {
for(int k = 0; k <= c; k++) {
for(int l = k; l <= c; l++) {
dp[i][k][j][l] = -1;
}
}
}
}
cout << calc(0, 0, r, c) << '\n';
}
