#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int n, m;
ll dp[51][51][51][51];
ll sc[51][51];
ll getqs(int i1, int j1, int i2, int j2) {
return sc[i2][j2] - sc[i1-1][j2] - sc[i2][j1-1] + sc[i1-1][j1-1];
}
ll rec(int i1, int j1, int i2, int j2) {
ll &cdp = dp[i1][j1][i2][j2];
if(~cdp) return cdp;
cdp = LLONG_MAX;
ll cqs = getqs(i1,j1,i2,j2);
for(int ik=i1;ik<i2;ik++)
cdp = min(cdp, cqs+rec(i1,j1,ik,j2)+rec(ik+1,j1,i2,j2));
for(int jk=j1;jk<j2;jk++)
cdp = min(cdp, cqs+rec(i1,j1,i2,jk)+rec(i1,jk+1,i2,j2));
return cdp;
}
int main() {
// your code goes here
cin >> n >> m;
for(int i=1;i<=n;i++ ) {
for(int j=1;j<=m;j++) {
cin >> sc[i][j];
sc[i][j] = sc[i][j] + sc[i-1][j] + sc[i][j-1] - sc[i-1][j-1];
}
}
memset(dp, -1, sizeof dp);
for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) dp[i][j][i][j]=0;
cout << rec(1,1,n,m);
return 0;
}
