#include <bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
#define pb push_back
#define ll long long
using namespace std;
int a[2001][2001];
int dp[51][51][51][51];
int solve(int l , int r , int L , int R){
if(l == r && L == R){
return 0;
}
if(l >r || L > R){
return 0;
}
if(dp[l][r][L][R] != -1) return dp[l][r][L][R];
int sum =0;
for(int i =l ; i<=r; i++){
for(int j = L; j<=R; j++){
sum+=a[i][j];
}
}
int res = 1e9;
for(int i = l ; i<=r-1; i++){
res = min(res , solve(l , i , L , R) + solve(i + 1 , r , L ,R) + sum);
}
for(int i = L; i<=R-1; i++){
res = min(res , solve(l , r , L , i) + solve(l, r , i + 1 , R) + sum);
}
return dp[l][r][L][R] = res;
}
int main (){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int n , m;
cin >> n >> m;
memset(dp , -1 , sizeof(dp));
for(int i = 1; i<=n; i++){
for(int j = 1; j<=m; j++){
cin >> a[i][j];
}
}
cout << solve(1 , n , 1 , m) << endl;
return 0;
}
