#include <bits/stdc++.h>
using namespace std;
#define int long long
#define forn(i,n) for(int i=0;i<n;++i)
#define pi pair<int,int>
#define f first
#define s second
#define pb push_back
#define all(x) x.begin(),x.end()
#define vii(a,n) vector<int>a(n);forn(i,n)cin>>a[i];
const int inf = 1e15;
const int N=50;
int dp[N][N][N][N];
int mem[N][N][N][N];
int pr[N+1][N+1];
int query(int a, int b, int c, int d) {
a++, b++, c++, d++;
return pr[c][d] - pr[c][b-1] - pr[a-1][d] + pr[a-1][b-1];
}
void rec(int a, int b, int c, int d) {
if (mem[a][b][c][d]) return;
mem[a][b][c][d]=1;
for (int m=a; m<c; ++m) {
rec(a,b,m,d); rec(m+1,b,c,d);
dp[a][b][c][d]=min(dp[a][b][c][d],dp[a][b][m][d]+dp[m+1][b][c][d]);
}
for (int m=b; m<d; ++m) {
rec(a,b,c,m); rec(a,m+1,c,d);
dp[a][b][c][d]=min(dp[a][b][c][d],dp[a][b][c][m]+dp[a][m+1][c][d]);
}
dp[a][b][c][d]+=query(a,b,c,d);
//cout<<a<<' '<<b<<' '<<c<<' '<<d<<" "<<dp[a][b][c][d]<<'\n';
}
void solve() {
int n,m; cin>>n>>m;
forn(i,n) forn(j,m) forn(k,n) forn(t,m) dp[i][j][k][t]=inf;
forn(i,n) forn(j,m) dp[i][j][i][j]=0;
forn(i,n) forn(j,m) mem[i][j][i][j]=1;
forn(i,n) {
forn(j,m) {
int x; cin>>x;
pr[i+1][j+1]=pr[i+1][j]+pr[i][j+1]-pr[i][j]+x;
//cout<<pr[i+1][j+1]<<' ';
}
//cout<<'\n';
}
rec(0,0,n-1,m-1);
cout<<dp[0][0][n-1][m-1]<<'\n';
}
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
solve();
}
