#include<bits/stdc++.h>
using namespace std;
vector<vector<int>> ps;
vector<vector<vector<vector<int>>>> dp;
int val(int a, int b, int c, int d){
return ps[b+1][d+1]-ps[a][d+1]-ps[b+1][c]+ps[a][c];
}
int solve(int a, int b, int c, int d){
if (a == b && c == d) return 0;
if (dp[a][b][c][d] != -1) return dp[a][b][c][d];
int bsf = pow(10, 8);
for (int i=a; i<b; i++) bsf = min(bsf, solve(a, i, c, d)+solve(i+1, b, c, d));
for (int i=c; i<d; i++) bsf = min(bsf, solve(a, b, c, i)+solve(a, b, i+1, d));
return dp[a][b][c][d] = bsf+val(a, b, c, d);
}
int main(){
int n, m;
cin >> n >> m;
ps.resize(n+1, vector<int>(m+1, 0));
for (int i=0; i<n; i++){
for (int j=0; j<m; j++){
cin >> ps[i+1][j+1];
ps[i+1][j+1] += (ps[i][j+1]+ps[i+1][j]-ps[i][j]);
}
}
dp.resize(n, vector<vector<vector<int>>>(n, vector<vector<int>>(m, vector<int>(m, -1))));
cout << solve(0, n-1, 0, m-1) << "\n";
}
