#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int n, m;
int mat[52][52];
ll prefix[52][52];
ll dp[52][52][52][52];
ll query(int x1, int y1, int x2, int y2) {
ll ans = 0;
ans += prefix[x2][y2];
ans -= prefix[x1-1][y2];
ans -= prefix[x2][y1-1];
ans += prefix[x1-1][y1-1];
return ans;
}
ll f(int x1, int y1, int x2, int y2) {
if(x1 > n || x2 > n || y1 > m || y2 > m) return 0;
if(x1 < 1 || x2 < 1 || y1 < 1 || y2 < 1) return 0;
if(x1 == x2 && y1 == y2) return 0;
if(dp[x1][y1][x2][y2] != -1) return dp[x1][y1][x2][y2];
ll ans = 1e16;
for(int i=x1; i<x2; i++)
ans = min(ans, f(x1, y1, i, y2) + f(i+1, y1, x2, y2));
for(int i=y1; i<y2; i++)
ans = min(ans, f(x1, y1, x2, i) + f(x1, i+1, x2, y2));
return dp[x1][y1][x2][y2] = ans + query(x1, y1, x2, y2);
}
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin >> n >> m;
memset(prefix, 0, sizeof(prefix));
memset(dp, -1, sizeof(dp));
for(int i=1; i<=n; i++)
for(int j=1; j<=m; j++)
cin >> mat[i][j];
//build prefix table
for(int i=1; i<=n; i++) {
for(int j=1; j<=m; j++) {
prefix[i][j] += mat[i][j];
prefix[i][j] += prefix[i-1][j];
prefix[i][j] += prefix[i][j-1];
prefix[i][j] -= prefix[i-1][j-1];
}
}
cout << f(1, 1, n, m) << '\n';
return 0;
}
