#pragma GCC optimize ("O3")
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,avx2,fma")
#include <bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
// author: amin_2008
#define ios ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define ll long long
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define pb push_back
#define bpc __builtin_popcount
#define pii pair<int, int>
#define pll pair<ll, ll>
#define piii pair<pii, int>
#define vpii vector<pii>
#define vpll vector<pll>
#define vvpii vector<vpii>
#define vvi vector<vector<int>>
#define vvl vector<vector<ll>>
#define ins insert
#define ts to_string
#define F first
#define S second
#define lb lower_bound
#define ub upper_bound
#define ld long double
#define ull unsigned long long
#define endl '\n'
#define int ll
using namespace std;
using namespace __gnu_pbds;
using namespace __cxx11;
template<class T> using ordered_set = tree<T, null_type,less<T>, rb_tree_tag,tree_order_statistics_node_update>;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int inf = 1e9;
const int mod = 1e9+7;
const int sz = 50;
const int N = 100005;
const int logg = 18;
const int P = 40000005;
const int M = 5e5+5;
int a[sz];
int dp[sz][sz][sz][sz], memo[sz][sz][sz][sz];
int pref[sz+1][sz+1];
int get(int a, int b, int c, int d)
{
a++;
b++;
c++;
d++;
return pref[c][d] - pref[c][b-1] - pref[a-1][d] + pref[a-1][b-1];
}
void wannabeDP(int a, int b, int c, int d)
{
if ( memo[a][b][c][d] ) return;
memo[a][b][c][d] = 1;
for(int i = a; i < c; i++)
wannabeDP(a, b, i, d),
wannabeDP(i+1, b, c, d),
dp[a][b][c][d] = min(dp[a][b][c][d], dp[a][b][i][d] + dp[i+1][b][c][d]);
for(int i = b; i < d; i++)
wannabeDP(a, b, c, i),
wannabeDP(a, i+1, c, d),
dp[a][b][c][d] = min(dp[a][b][c][d], dp[a][b][c][i] + dp[a][i+1][c][d]);
dp[a][b][c][d] += get(a, b, c, d);
}
void solve()
{
int n, m;
cin >> n >> m;
for(int i = 0; i < n; i++)
{
for(int j = 0; j < m; j++)
{
for(int k = 0; k < n; k++)
{
for(int t = 0; t < m; t++)
{
dp[i][j][k][t] = 1e15;
}
}
}
}
for(int i = 0; i < n; i++)
for(int j = 0; j < m; j++)
dp[i][j][i][j] = 0;
for(int i = 0; i < n; i++)
for(int j = 0; j < m; j++)
memo[i][j][i][j] = 1;
for(int i = 0; i < n; i++)
for(int j = 0, x; j < m; j++)
cin >> x,
pref[i+1][j+1] = pref[i+1][j] + pref[i][j+1] - pref[i][j] + x;
wannabeDP(0, 0, n - 1, m - 1);
cout << dp[0][0][n-1][m-1] << endl;
}
signed main()
{
ios;
//precompute();
int t = 1;
//cin >> t;
while(t--){
solve();
}
}
