#include <bits/stdc++.h>
using namespace std;
vector<vector<vector<vector<int>>>> dp;
vector<vector<int>> ps;
// minimum cost to cut a piece of chocolate completely with corners at (i, j) and (k, l)
int cut(int i, int j, int k, int l) {
if (i == k && j == l)
return 0;
if (dp[i][j][k][l] != -1)
return dp[i][j][k][l];
int x = ps[k][l]-ps[k][j-1]-ps[i-1][l]+ps[i-1][j-1];
int ans = INT_MAX;
// only one row left
if (i == k) {
// only two columns left
if (j+1 == l)
return x;
for (int col = j; col < l; col++) {
ans = min(ans, x+cut(i, j, k, col)+cut(i, col+1, k, l));
}
}
// only one column left
else if (j == l) {
// only two rows left
if (i+1 == k)
return x;
for (int row = i; row < k; row++) {
ans = min(ans, x+cut(i, j, row, l)+cut(row+1, j, k, l));
}
}
else {
// iterate over all horizontal cuts
for (int h = i; h < k; h++) {
ans = min(ans, x+cut(i, j, h, l)+cut(h+1, j, k, l));
}
// iterate over all vertical cuts
for (int v = j; v < l; v++) {
ans = min(ans, x+cut(i, j, k, v)+cut(i, v+1, k, l));
}
}
if (ans == INT_MAX)
ans = x;
return dp[i][j][k][l] = ans;
}
int main() {
int n, m;
cin >> n >> m;
vector<vector<int>> grid(n+1, vector<int>(m+1));
ps.resize(n+1, vector<int>(m+1));
dp.resize(n+1, vector<vector<vector<int>>>(m+1, vector<vector<int>>(n+1, vector<int>(m+1, -1))));
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> grid[i][j];
}
}
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
ps[i][j] += ps[i][j-1]+grid[i][j];
}
for (int j = 1; j <= m; j++) {
ps[i][j] += ps[i-1][j];
}
}
cout << cut(1, 1, n, m) << '\n';
return 0;
}
