#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define FOR(i,N) for(ll i = 0; i < N; i++)
#define all(x) (x).begin(), (x).end()
#define F first
#define S second
int N, M;
vector<vector<vector<vector<int>>>> dp;
vector<vector<int>> ras;
int solve(int a, int b, int c, int d) {
if (a == b && c == d) return 0;
if (dp[a][b][c][d] != INT_MIN) return dp[a][b][c][d];
int mn = 1e8;
for(int i = a; i < b; i++) mn = min(mn, solve(a, i, c, d) + solve(i + 1, b, c, d));
for(int i = c; i < d; i++) mn = min(mn, solve(a, b, c, i) + solve(a, b, i + 1, d));
return dp[a][b][c][d] = mn + ras[b+1][d+1] - ras[b+1][c] - ras[a][d+1] + ras[a][c];
}
signed main() {
cin.tie(0); ios::sync_with_stdio(false);
cin >> N >> M;
ras.resize(N+1, vector<int>(M+1));
dp.resize(N, vector<vector<vector<int>>>(N, vector<vector<int>>(M, vector<int>(M, INT_MIN))));
FOR(r, N) {
FOR(c, M) {
cin >> ras[r+1][c+1];
ras[r+1][c+1] += ras[r][c+1] + ras[r+1][c] - ras[r][c];
}
}
cout << solve(0,N-1,0,M-1);
}
