#include <bits/stdc++.h>
#define pb push_back
#define eb emplace_back
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define uniq(x) x.erase(unique(all(x)), x.end())
#define rall(x) x.rbegin(), x.rend()
//#define int long long
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int mod = 1e9 + 7;
const int LOG = 20;
const int maxn = 1e5 + 5;
const double eps = 1e-9;
void setIO() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
}
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 == x2 && y1 == y2) return 0;
if(dp[x1][y1][x2][y2] != -1) return dp[x1][y1][x2][y2];
//cout << "(" << x1 << " " << y1 << "), (" << x2 << " " << y2 << ")\n";
ll ans = 1e18;
//make horizontal cut
for(int i=x1; i<x2; i++) {
ans = min(ans, f(x1, y1, i, y2) + f(i+1, y1, x2, y2));
}
//make vertical cut
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][y1] = ans + query(x1, y1, x2, y2);
}
int32_t main() {
setIO();
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;
}
