#include <bits/stdc++.h>
using namespace std;
#define int long long
#define N 51
int dp[N][N][N][N], a[N][N], ps[N][N];
int query(int x1, int y1, int x2, int y2) {
return (ps[x2][y2] + ps[x1 - 1][y1 - 1] + ps[x1 - 1][y2] - ps[x2][y1 - 1]);
}
int solve(int a, int b, int c, int d) {
if (dp[a][b][c][d] != -1) return dp[a][b][c][d];
int mn = 1e18;
for (int i = a + 1; i <= c; i++) {
mn = min(mn, solve(a, b, i - 1, d) + solve(i, b, c, d));
}
for (int i = b + 1; i <= d; i++) {
mn = min(mn, solve(a, b, c, i - 1) + solve(a, i, c, d));
}
dp[a][b][c][d] = (mn + query(a, b, c, d));
return dp[a][b][c][d];
}
signed main() {
ios::sync_with_stdio(0); cin.tie(0);
int n, m; cin >> n >> m;
for (int i = 0; i < N; i++) for (int j = 0; j < N; j++) for (int k = 0; k < N; k++) for (int l = 0; l < N; l++) dp[i][j][k][l] = -1;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> a[i][j];
dp[i][j][i][j] = 0;
}
}
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
if (i == 1 && j == 1) {
ps[i][j] = a[i][j];
} else {
ps[i][j] = a[i][j] + ps[i - 1][j] + ps[i][j - 1] - ps[i - 1][j - 1];
}
}
}
cout << solve(1, 1, n, m) << "\n";
return 0;
}
