#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 52;
ll n,m,a[N][N];
ll pf[N][N];
ll dp[N][N][N][N];
ll suma(int i,int j,int h,int g){
return (pf[h][g]-pf[i-1][g]-pf[h][j-1]+pf[i-1][j-1]);
}
int daj(int a,int b,int c,int d){
if(dp[a][b][c][d] != -1) return dp[a][b][c][d];
ll uksum = suma(a,b,c,d);
ll minv = 7e18;
for(int i = b; i < d; i++){
minv = min(minv,daj(a,b,c,i)+daj(a,i+1,c,d)+uksum);
}
ll minh = 7e18;
for(int i = a; i < c; i++){
minh = min(minh,daj(a,b,i,d)+daj(i+1,b,c,d)+uksum);
}
return dp[a][b][c][d] = min(minv,minh);
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> n >> m;
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
cin >> a[i][j];
}
}
for(int j = 1; j <= m; j++) pf[1][j] = pf[1][j-1]+a[1][j];
for(int i = 1; i <= n; i++) pf[i][1] = pf[i-1][1]+a[i][1];
for(int i = 2; i <= n; i++){
for(int j = 2; j <= m; j++){
pf[i][j] = pf[i][j-1]+pf[i-1][j]-pf[i-1][j-1]+a[i][j];
}
}
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
for(int h = i; h <= n; h++){
for(int g = j; g <= m; g++){
if(i == h && j == g) dp[i][j][h][g] = 0;
else dp[i][j][h][g] = -1;
}
}
}
}
cout << daj(1,1,n,m) << endl;
}
