// - 12/2/23
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <numeric>
#include <cmath>
#include <iterator>
#include <set>
#include <map>
#include <math.h>
#include <iomanip>
#include <unordered_set>
#include <queue>
#include <climits>
using namespace std;
// clang++ -std=c++17 IOI09_Raisins.cpp && ./a.out
using ll = long long;
int n, m;
vector<vector<int>> grid, pref;
const int MAXN = 50;
int dp[MAXN][MAXN][MAXN][MAXN];
int sum(int x1, int y1, int x2, int y2){
x2++;
y2++;
return pref[x2][y2] - pref[x2][y1] - pref[x1][y2] + pref[x1][y1];
}
int get(int x1, int y1, int x2, int y2){
if (dp[x1][y1][x2][y2] != -1) return dp[x1][y1][x2][y2];
if (x1 == x2 && y1 == y2) return 0;
int res = INT_MAX;
// horizontal cuts
for (int i = x1; i < x2; i++){
res = min(res, get(x1, y1, i, y2) + get(i + 1, y1, x2, y2) + sum(x1, y1, i, y2) + sum(i + 1, y1, x2, y2));
}
// vertical cuts
for (int j = y1; j < y2; j++){
res = min(res, get(x1, y1, x2, j) + get(x1, j + 1, x2, y2) + sum(x1, y1, x2, j) + sum(x1, j + 1, x2, y2));
}
dp[x1][y1][x2][y2] = res;
// cout << x1 << ' ' << y1 << ' ' << x2 << ' ' << y2 << ' ' << res << '\n';
return res;
}
void solve(){
cin >> n >> m;
grid.resize(n, vector<int> (m));
pref.resize(n + 1, vector<int> (m + 1));
for (int i = 0; i < MAXN; i++){
for (int j = 0; j < MAXN; j++){
for (int k = 0; k < MAXN; k++){
for (int l = 0; l < MAXN; l++) dp[i][j][k][l] = -1;
}
}
}
for (int i = 0; i < n; i++){
for (int j = 0; j < m; j++) cin >> grid[i][j];
}
for (int i = 1; i <= n; i++){
for (int j = 1; j <= m; j++){
pref[i][j] = grid[i-1][j-1] + pref[i-1][j] + pref[i][j-1] - pref[i-1][j-1];
}
}
cout << get(0, 0, n - 1, m - 1);
cout << '\n';
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
// freopen("input.txt", "r", stdin);
solve();
return 0;
}
