#pragma GCC optimize("O3,inline")
#include <bits/stdc++.h>
using namespace std;
#define F(i, n) for(int i = 0; i < (n); i++)
#define FF(i, s, n) for(int i = s; i < (n); i++)
#define F_reverse(i, n) for(int i = (n) - 1; i >= 0; i--)
#define dcout if(0) cout
#define N 50 + 1
int32_t grid_sum[N][N];
int32_t dp[N][N][N][N];
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, m;
cin >> n >> m;
FF(i, 1, n + 1) {
FF(j, 1, m + 1) {
cin >> grid_sum[i][j];
grid_sum[i][j] += grid_sum[i][j - 1];
}
FF(j, 1, m + 1) {
grid_sum[i][j] += grid_sum[i - 1][j];
}
}
FF(h, 1, n + 1) {
FF(w, 1, m + 1) {
if(h == 1 && w == 1) {
continue;
}
F(r, n - h + 1) {
F(c, m - w + 1) {
int32_t cost = grid_sum[r + h][c + w];
cost -= grid_sum[r][c + w];
cost -= grid_sum[r + h][c];
cost += grid_sum[r][c];
int32_t subproblem_costs = INT32_MAX;
FF(split_width, 1, w) {
subproblem_costs = min(subproblem_costs, dp[h][split_width][r][c] + dp[h][w - split_width][r][c + split_width]);
}
FF(split_height, 1, h) {
subproblem_costs = min(subproblem_costs, dp[split_height][w][r][c] + dp[h - split_height][w][r + split_height][c]);
}
dp[h][w][r][c] = cost + subproblem_costs;
}
}
}
}
cout << dp[n][m][0][0] << '\n';
}
