#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
typedef long long ll;
typedef pair<long long, long long> pll;
typedef pair<int,int> pii;
typedef vector<long long> vl;
typedef vector<int> vi;
int n, m;
ll mat[55][55], dp[55][55][55][55], pref[55][55];
// dp(i,j,k,l) minimum raisins to cut rectangle(i,j) up to(k,l);
ll f(int x1, int x2, int y1, int y2){
if(x1 == x2 && y1 == y2) return 0;
if(dp[x1][x2][y1][y2] != -1) return dp[x1][x2][y1][y2];
ll ans = 1e18;
for(int i=x1; i < x2;i++){
ans = min(ans, f(x1, i, y1, y2) + f(i+1, x2, y1, y2));
}
for(int i = y1; i < y2; i++){
ans = min(ans, f(x1, x2, y1, i) + f(x1, x2, i+1, y2));
}
return dp[x1][x2][y1][y2] = ans + (pref[x2][y2] - pref[x1-1][y2] - pref[x2][y1-1] + pref[x1-1][y1-1]);
}
int main(){
cin>>n>>m;
for(int i = 1; i <= n; i++)
for(int j = 1; j <= m; j++)
cin>>mat[i][j];
memset(dp, -1, sizeof dp);
memset(pref, 0, sizeof pref);
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
pref[i][j] = pref[i-1][j] + pref[i][j-1] + mat[i][j] - pref[i-1][j-1];
}
}
cout<<f(1, n, 1, m)<<endl;
return 0;
}
