/***********************************************
* auth: tapilyoca *
* date: 06/09/2025 at 11:11:32 *
* dots: https://github.com/tapilyoca/dotilyoca *
***********************************************/
#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9+7;
template<typename T>
using vec = vector<T>;
using ll = long long;
using vll = vec<ll>;
using vvll = vec<vll>;
using pll = pair<ll,ll>;
using str = string;
#define pb push_back
#define dbg(x) cerr << #x << ": " << x << endl;
/***********************************************/
ll n, m;
ll memo[55][55][55][55];
vvll grid;
vvll pref;
inline ll rect_sum(ll ti, ll tj, ll bi, ll bj) {
ll out = pref[bi][bj];
if(ti == tj and ti == 0) return out;
if(ti == 0) return out - pref[bi][tj-1];
if(tj == 0) return out - pref[ti-1][bj];
return out - pref[bi][tj-1] - pref[ti-1][bj] + pref[ti-1][tj-1];
}
ll dp(ll ti, ll tj, ll bi, ll bj) {
// returns ans for rectangle with tl corner at [ti][tj] and br corner at [bi][bj], all inclusive.
if(memo[ti][tj][bi][bj] != -1) {
return memo[ti][tj][bi][bj];
}
// base case: 1 x 1
if(ti == bi and tj == bj) {
return memo[ti][tj][bi][bj] = 0;
}
// base case: 1 x 2
if((bi == ti + 1 and bj == tj) or (bi == ti and bj == tj + 1)) {
return memo[ti][tj][bi][bj] = grid[ti][tj] + grid[bi][bj];
}
ll min_hori = 1e18, min_verti = 1e18;
// checking all horizontal cuts:
for(int i = ti; i < bi; i++) {
min_hori = min(min_hori, dp(ti,tj,i,bj) + dp(i+1,tj,bi,bj) + rect_sum(ti,tj,bi,bj));
}
// checking all vertical cuts:
for(int i = tj; i < bj; i++) {
min_verti = min(min_verti, dp(ti,tj,bi,i) + dp(ti,i+1,bi,bj) + rect_sum(ti,tj,bi,bj));
}
return memo[ti][tj][bi][bj] = min(min_hori,min_verti);
}
void solve(){
cin >> n >> m;
grid.assign(n, vll(m,0));
pref.assign(n, vll(m,0));
memset(memo,-1,sizeof(memo));
for(int i = 0; i < n; i++) {
for(int j = 0; j < m; j++) {
cin >> grid[i][j];
}
}
for(int i = 0; i < n; i++) {
for(int j = 0; j < m; j++) {
pref[i][j] = grid[i][j];
if(i) pref[i][j] += pref[i-1][j];
if(j) pref[i][j] += pref[i][j-1];
if(i and j) pref[i][j] -= pref[i-1][j-1];
}
}
cout << dp(0ll,0ll,n-1,m-1) << endl;
}
int main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
int t = 1;
while(t--){
solve();
}
return 0;
}
/*
| 1 | 2 | 3 | 4
0| -------------
| 5 | 6 | 7 | 8
1| -------------
| 9 | A | B | C
-----------------
0 1 2
*/
