#include <bits/stdc++.h>
using namespace std;
#define REP(a,i,n) for (int i=a;i<n;i++)
#define ll long long
ll choc[51][51];
ll func(int a, int b, int x, int y) {
if (a==x && b==y) {
return 0;
}
ll mini = 1e9, cur = choc[x][y] + choc[a-1][b-1] - choc[a-1][y] - choc[x][b-1];
//cout << a << ' ' << b << ' ' << x << ' ' << y << ": " <<cur << endl;
REP(a, i, x) {
mini = min(mini, func(a, b, i, y) + func(i+1, b, x, y));
}
REP(b, j, y) {
mini = min(mini, func(a, b, x, j) + func(a, j+1, x, y));
}
return mini + cur;
}
void prefixing(int n, int m) {
REP(1, i, n+1) {
REP(1, j, m+1) {
choc[i][j]+= choc[i][j-1];
}
}
REP(1, j, m+1) {
REP(1, i, n+1) {
choc[i][j]+= choc[i-1][j];
}
}
}
int main() {
int n, m; cin >> n >> m;
REP(1, i, n+1) {
REP(1, j, m+1) {
cin >> choc[i][j];
}
}
prefixing(n, m);
cout << func(1, 1, n, m);
return 0;
}
