#include <bits/stdc++.h>
using namespace std;
const int N=51;
int f[N][N][N][N], pf[N][N], a[N][N], n, m;
int dp(int x1, int y1, int x2, int y2){
if (f[x1][y1][x2][y2]!=-1) return f[x1][y1][x2][y2];
if (x1==x2 && y1==y2) return f[x1][y1][x2][y2]=0;
int sum=pf[x2][y2]-pf[x1-1][y2]-pf[x2][y1-1]+pf[x1-1][y1-1];
int ans=1e9;
for (int x=x1; x<x2; ++x){
ans=min(ans, dp(x1, y1, x, y2)+dp(x+1, y1, x2, y2)+sum);
}
for (int y=y1; y<y2; ++y){
ans=min(ans, dp(x1, y1, x2, y)+dp(x1, y+1, x2, y2)+sum);
}
return f[x1][y1][x2][y2]=ans;
}
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> m;
for (int i=1; i<=n; ++i) for (int j=1; j<=m; ++j){
cin >> a[i][j];
pf[i][j]=pf[i-1][j]+pf[i][j-1]-pf[i-1][j-1]+a[i][j];
}
memset(f, -1, sizeof f);
cout << dp(1, 1, n, m) << '\n';
return 0;
}
