include<bits/stdc++.h>

using namespace std;

define int long long int

define endl '\n'

int n,m; int arr[50][50]; int dpsum[50][50][50][50]; int dp[50][50][50][50]; vector<vector> prefix_sum;

int sum(int rowup,int rowdown,int colleft,int colright){ // cout<<rowup<<" "<<rowdown<<" "<<colleft<<" "<<colright<<endl;

if(dpsum[rowup][rowdown][colleft][colright]!=-1) return dpsum[rowup][rowdown][colleft][colright];
int val=0;
if(rowup>0 && colleft>0) val=(prefix_sum[rowup - 1][colleft - 1]);

// cout<<val<<endl;
// cout<<(prefix_sum[rowdown][colright])<<endl;
// cout<<(rowup==0?0:prefix_sum[rowup - 1][colright])<<endl;
// cout<<(colleft==0?0:prefix_sum[rowdown][colleft - 1])<<endl;
// cout<<val<<endl;
return dpsum[rowup][rowdown][colleft][colright]=(prefix_sum[rowdown][colright]) - (rowup==0?0:prefix_sum[rowup - 1][colright]) -(colleft==0?0:prefix_sum[rowdown][colleft - 1]) + val;

}

int rec(int rowup,int rowdown,int colleft,int colright){ if(rowup==rowdown && colleft==colright){ return 0; }

if(dp[rowup][rowdown][colleft][colright]!=-1) return dp[rowup][rowdown][colleft][colright];

// cout<<rowup<<" "<<rowdown<<" "<<colleft<<" "<<colright<<endl;

int ans=1e18;
for(int i=rowup;i<rowdown;i++){
    // cout<<sum(rowup,rowdown,colleft,colright)<<endl;
    ans=min(ans, sum(rowup,rowdown,colleft,colright) + rec(rowup,i,colleft,colright) + rec(i+1,rowdown,colleft,colright));
}

for(int i=colleft;i<colright;i++){
    // cout<<sum(rowup,rowdown,colleft,colright)<<endl;
    ans=min(ans, sum(rowup,rowdown,colleft,colright) + rec(rowup,rowdown,colleft,i) +rec(rowup,rowdown,i+1,colright));
}

// cout<<rowup<<" "<<rowdown<<" "<<colleft<<" "<<colright<<" "<<ans<<endl;

return dp[rowup][rowdown][colleft][colright]=ans;

}

void solve(){ cin>>n>>m; for(int i=0;i<n;i++){ for(int j=0;j<m;j++){ cin>>arr[i][j]; } }

memset(dp,-1,sizeof(dp));
memset(dpsum,-1,sizeof(dpsum));


prefix_sum=vector<vector<int>>(n,vector<int>(m,0));

// vector<vector<int>> prefix_sum(n, vector<int>(m));

prefix_sum[0][0] = arr[0][0];
for(int i = 1; i < n; i++) {
    prefix_sum[i][0] = prefix_sum[i - 1][0] + arr[i][0];
}
for(int j = 1; j < m; j++) {
    prefix_sum[0][j] = prefix_sum[0][j - 1] + arr[0][j];
}
for(int i = 1; i < n; i++) {
    for(int j = 1; j < m; j++) {
        prefix_sum[i][j] = arr[i][j] + prefix_sum[i - 1][j] + prefix_sum[i][j - 1] - prefix_sum[i - 1][j - 1];
    }
}

// for(int i = 0; i < n; i++) {
//     for(int j = 0; j < m; j++) {
//         cout << prefix_sum[i][j] << ' ';
//     }
//     cout << endl;
// }

cout<<rec(0,n-1,0,m-1);

} int32_t main(){ ios_base::sync_with_stdio(0); cin.tie(0);cout.tie(0);

//int _t; cin>>_t; while(_t--)
solve();
return 0;

}