#include <bits/stdc++.h>
using namespace std;
int sum(const vector<vector<int>>& mat2,int x1,int y1,int x2,int y2){
if (x1==0 && y1==0){
return mat2[y2][x2];
}
else if(x1==0){
return mat2[y2][x2]-mat2[y1-1][x2];
}
else if(y1==0){
return mat2[y2][x2]-mat2[y2][x1-1];
}
else{
return mat2[y2][x2]-mat2[y1-1][x2]-mat2[y2][x1-1]+mat2[y1-1][x1-1];
}
}
int rek(const vector<vector<int>>& mat,const vector<vector<int>>& mat2,vector<vector<vector<vector<int>>>>& mem,int x1,int y1,int x2,int y2){
if (x1==x2 && y1==y2){
return 0;
}
if (mem[x1][y1][x2][y2]!=-1){
return mem[x1][y1][x2][y2];
}
int najm=numeric_limits<int>::max();
for (int i=x1;i<x2;i++){
int pom=rek(mat,mat2,mem,x1,y1,i,y2);
int pom2=rek(mat,mat2,mem,i+1,y1,x2,y2);
najm=min(najm,pom+pom2);
}
for (int i=y1;i<y2;i++){
int pom=rek(mat,mat2,mem,x1,y1,x2,i);
int pom2=rek(mat,mat2,mem,x1,i+1,x2,y2);
najm=min(najm,pom+pom2);
}
mem[x1][y1][x2][y2]=najm+sum(mat2,x1,y1,x2,y2);
return najm+sum(mat2,x1,y1,x2,y2);
}
int main(){
int n;
int m;
cin >> n >> m;
vector<vector<int>> mat={};
for (int i=0;i<n;i++){
mat.push_back({});
for (int j=0;j<m;j++){
int unos;
cin >> unos;
mat[i].push_back(unos);
}
}
vector<vector<int>> mat2={};
for (int i=0;i<n;i++){
mat2.push_back({});
for (int j=0;j<m;j++){
if (i==0 && j==0){
mat2[i].push_back(mat[i][j]);
}
else if(i==0){
mat2[i].push_back(mat[i][j]+mat2[i][j-1]);
}
else if(j==0){
mat2[i].push_back(mat[i][j]+mat2[i-1][j]);
}
else{
mat2[i].push_back(mat[i][j]+mat2[i][j-1]+mat2[i-1][j]-mat2[i-1][j-1]);
}
}
}
vector<vector<vector<vector<int>>>> mem=vector<vector<vector<vector<int>>>>(m,vector<vector<vector<int>>>(n,vector<vector<int>>(m,vector<int>(n,-1))));
// cout << sum(mat2,0,1,2,3) << "\n";
cout << rek(mat,mat2,mem,0,0,m-1,n-1) << "\n";
}
