#include <iostream>
using namespace std;
int n,m,a[55][55],pd[55][55][55][55];
int main()
{
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=1;i<=n;++i)
for(int j=1;j<=m;++j)
for(int ii=1;ii<=n;++ii)
for(int jj=1;jj<=m;++jj)
pd[i][j][ii][jj]=1000000000;
for(int l=1;l<=n;++l)
for(int c=1;c<=m;++c)
for(int i=1;i+l-1<=n;++i)
for(int j=1;j+c-1<=m;++j)
{
int ii=i+l-1;
int jj=j+c-1;
if(i==ii&&j==jj)
pd[i][j][ii][jj]=0;
else
{
for(int iii=i+1;iii<=ii;++iii)
pd[i][j][ii][jj]=min(pd[i][j][ii][jj],pd[i][j][iii-1][jj]+pd[iii][j][ii][jj]);
for(int jjj=j+1;jjj<=jj;++jjj)
pd[i][j][ii][jj]=min(pd[i][j][ii][jj],pd[i][j][ii][jjj-1]+pd[i][jjj][ii][jj]);
pd[i][j][ii][jj]+=a[ii][jj]-a[i-1][jj]-a[ii][j-1]+a[i-1][j-1];
}
}
cout<<pd[1][1][n][m];
return 0;
}
