#include <bits/stdc++.h>
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define pb push_back
using namespace std;
typedef long long ll;
typedef pair <ll, ll> pii;
const int N = 57;
int n, m;
ll mat[N][N], ps[N][N];
ll dp[N][N][N][N];
ll f(int a1, int b1, int a2, int b2) {
return ps[a2][b2] - ps[a1-1][b2] - ps[a2][b1-1] + ps[a1-1][b1-1];
}
ll DP(int a1, int b1, int a2, int b2) {
if (dp[a1][b1][a2][b2] != -1) return dp[a1][b1][a2][b2];
if (a1 == a2 && b1 == b2) {
dp[a1][b1][a2][b2] = 0;
return 0;
}
ll mn = 1e18;
for (int i = a1; i < a2; i++) {
mn = min(mn, DP(a1, b1, i, b2) + DP(i+1, b1, a2, b2));
}
for (int i = b1; i < b2; i++) {
mn = min(mn, DP(a1, b1, a2, i) + DP(a1, i+1, a2, b2));
}
dp[a1][b1][a2][b2] = mn + f(a1, b1, a2, b2);
return dp[a1][b1][a2][b2];
}
int main () {
memset(dp, -1, sizeof dp);
cin >> n >> m;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> mat[i][j];
ps[i][j] = ps[i-1][j] + ps[i][j-1] - ps[i-1][j-1] + mat[i][j];
}
}
cout << DP(1, 1, n, m);
return 0;
}
