/**
* author: milos
* created: 10.01.2021 02:07:32
**/
#include <bits/stdc++.h>
using namespace std;
const int N = 51;
int n, m;
vector<vector<int>> a(N, vector<int>(N));
vector<vector<vector<vector<long long>>>> dp(N, vector<vector<vector<long long>>>(N, vector<vector<long long>>(N, vector<long long>(N, 0))));
long long Calc(int x1, int y1, int x2, int y2) {
if (x1 == x2 && y1 == y2) {
return 0LL;
}
if (dp[x1][y1][x2][y2] != 0) {
return dp[x1][y1][x2][y2];
}
//cout << x1 << " " << y1 << " " << x2 << " " << y2 << '\n';
long long ans = 1e18, sum = 0;
for (int i = x1; i <= x2; i++) {
for (int j = y1; j <= y2; j++) {
sum += a[i][j];
}
}
for (int i = x1 + 1; i <= x2; i++) {
ans = min(ans, Calc(x1, y1, i - 1, y2) + Calc(i, y1, x2, y2));
}
for (int i = y1 + 1; i <= y2; i++) {
ans = min(ans, Calc(x1, y1, x2, i - 1) + Calc(x1, i, x2, y2));
}
ans += sum;
dp[x1][y1][x2][y2] = ans;
return ans;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n >> m;
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
cin >> a[i][j];
}
}
cout << Calc(0, 0, n - 1, m - 1) << '\n';
return 0;
}
