#include <bits/stdc++.h>
using namespace std;
#define FIO ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define ll long long
#define pb push_back
#define fi first
#define se second
const int N = 55;
const ll MOD = 1e9 + 7;
const ll INF = 1e9;
int r[N][N];
int dp[N][N][N][N];
int cut(int x1, int y1, int x2, int y2){
if(x1==x2 && y1==y2) return 0;
if(dp[x1][y1][x2][y2]!=-1) return dp[x1][y1][x2][y2];
int b=INF;
for(int i=x1; i<x2; i++){
b=min(b,cut(x1,y1,i,y2)+cut(i+1,y1,x2,y2));
}
for(int i=y1; i<y2; i++){
b=min(b,cut(x1,y1,x2,i)+cut(x1,i+1,x2,y2));
}
dp[x1][y1][x2][y2]=b+r[x2][y2]+r[x1-1][y1-1]-r[x2][y1-1]-r[x1-1][y2];
return dp[x1][y1][x2][y2];
}
int main(){
FIO;
int n,m;
cin>>n>>m;
for(int i=1; i<=n; i++){
for(int j=1; j<=m; j++){
cin>>r[i][j];
r[i][j]+=r[i-1][j]+r[i][j-1]-r[i-1][j-1];
}
}
for(int i=1; i<=n; i++){
for(int j=1; j<=m; j++){
for(int i2=1; i2<=n; i2++){
for(int j2=1; j2<=m; j2++){
dp[i][j][i2][j2]=-1;
}
}
}
}
cout<<cut(1,1,n,m);
return 0;
}
