#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define FOR(i, a, b) for(ll i = a; i <= b; i++)
#define MAXD 55
#define f first
#define s second
ll n, m, r[MAXD][MAXD], dp[MAXD][MAXD][MAXD][MAXD], R = LONG_LONG_MAX;
int main(){
cin >> n >> m;
FOR(i, 0, MAXD - 1) FOR(j, 0, MAXD - 1) {
r[i][j] = 0;
FOR(i2, 0, MAXD - 1) FOR(j2, 0, MAXD - 1) dp[i][j][i2][j2] = LLONG_MAX;
}
FOR(i, 1, n) FOR(j, 1, m) {
cin >> r[i][j];
r[i][j] += r[i - 1][j] + r[i][j - 1] - r[i - 1][j - 1];
dp[i][j][i][j] = 0;
}
FOR(h, 1, n) FOR(w, 1, m){
if(h == w && h == 1) continue;
FOR(bl_h, 1, n - h + 1) FOR(bl_w, 1, m - w + 1) {
pair<ll, ll> bl = {bl_h, bl_w}, tr = {bl_h + h - 1, bl_w + w - 1};
ll cr = r[tr.f][tr.s] - r[tr.f][bl.s - 1] - r[bl.f - 1][tr.second] + r[bl.f - 1][bl.s - 1];
// horizontal cut
FOR(i, 1, h - 1){
dp[bl.f][bl.s][tr.f][tr.s] = min(dp[bl.f][bl.s][tr.f][tr.s], cr + dp[bl.f][bl.s][bl.f + i - 1][tr.s] + dp[bl.f + i][bl.s][tr.f][tr.s]);
}
// vertical cut
FOR(i, 1, w - 1){
dp[bl.f][bl.s][tr.f][tr.s] = min(dp[bl.f][bl.s][tr.f][tr.s], cr + dp[bl.f][bl.s][tr.f][bl.s + i - 1] + dp[bl.f][bl.s + i][tr.f][tr.s]);
}
//cout << "{(" << bl.f << ", " << bl.s << "), (" << tr.f << ", " << tr.s << ")} - dp: " << dp[bl.f][bl.s][tr.f][tr.s] << endl;
}
}
cout << dp[1][1][n][m] << endl;
}
