#include <bits/stdc++.h>
using namespace std;
#define INF 1000000000
int pre[51][51];
int dp[51][51][51][51];
int solve(int u, int l, int d, int r) {
if (dp[u][l][d][r] > 0) {
return dp[u][l][d][r];
}
if (u == d && l == r) {
return 0;
}
dp[u][l][d][r] = INF;
for (int x = u; x < d; x++) {
dp[u][l][d][r] = min(dp[u][l][d][r], solve(u, l, x, r) + solve(x + 1, l, d, r));
}
for (int y = l; y < r; y++) {
dp[u][l][d][r] = min(dp[u][l][d][r], solve(u, l, d, y) + solve(u, y + 1, d, r));
}
dp[u][l][d][r] += pre[d][r] - pre[u - 1][r] - pre[d][l - 1] + pre[u - 1][l - 1];
return dp[u][l][d][r];
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int N, M;
cin >> N >> M;
int v[51][51] = {};
for (int i = 1; i <= N; i++) {
for (int j = 1; j <= M; j++) {
cin >> v[i][j];
}
}
for (int i = 1; i <= N; i++) {
for (int j = 1; j <= M; j++) {
pre[i][j] = pre[i][j - 1] + v[i][j];
}
for (int j = 1; j <= M; j++) {
pre[i][j] += pre[i - 1][j];
}
}
cout << solve(1, 1, N, M) << '\n';
}
