#include<bits/stdc++.h>
#define int long long
using namespace std;
inline void chmin(int &a, int b)
{
a = min(a, b);
}
int a[55][55], dp[55][55][55][55];
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, m; cin>>n>>m;
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
cin>>a[i][j];
a[i][j] += a[i-1][j] + a[i][j-1] - a[i-1][j-1];
}
}
for(int i = n; i >= 1; i--){
for(int j = i; j <= n; j++){
for(int k = m; k >= 1; k--){
for(int l = k; l <= m; l++) if(i < j || k < l){
int sum = a[j][l] - a[i-1][l] - a[j][k-1] + a[i-1][k-1];
int &val = dp[i][j][k][l]; val = 1e18;
for(int m = i; m < j; m++) chmin(val, dp[i][m][k][l] + dp[m+1][j][k][l]);
for(int m = k; m < l; m++) chmin(val, dp[i][j][k][m] + dp[i][j][m+1][l]);
val += sum;
}
}
}
}
cout<<dp[1][n][1][m];
}
