#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned int ul;
typedef unsigned long long ull;
#define MASK(i) (1ULL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
ll gcd(ll a, ll b){return __gcd(a, b);}
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ll mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if (a < b) {a = b; return true;}
return false;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if (a > b) {a = b; return true;}
return false;
}
template <class T>
void printArr(T the_array_itself, string separator = " ", string finish = "\n", ostream &out = cout){
for(auto item: the_array_itself) out << item << separator;
out << finish;
}
template <class T>
void remove_dup(vector<T> &a){
sort(ALL(a));
a.resize(unique(ALL(a)) - a.begin());
}
const int N = 55, INF = 1e9 + 69;;
int a[N][N];
int dp[N][N][N][N];
int go(int u, int v, int x, int y){
int ans = a[x][y] - a[u-1][y] - a[x][v-1] + a[u-1][v-1];
if (u == x && v == y) return 0;
if (dp[u][v][x][y] != -1) return dp[u][v][x][y];
// cout << u << " " << v << " " << x << " " << y << " " << ans << "\n";
int mi = INF;
for(int i = u; i < x; ++i){
minimize(mi, go(u, v, i, y) + go(i + 1, v, x, y));
}
for(int i = v; i < y; ++i) {
minimize(mi, go(u, v, x, i) + go(u, i + 1, x, y));
}
return dp[u][v][x][y] = ans + mi;
}
void solve(){
int n, m; cin >> n >> m;
for(int i= 1; i<=n; ++i) for(int j = 1;j<=m; ++j){
cin >> a[i][j];
a[i][j] += a[i-1][j] + a[i][j-1] - a[i-1][j-1];
}
memset(dp, -1, sizeof dp);
cout << go(1, 1, n, m) << "\n";
}
int main(void){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
clock_t start = clock();
solve();
cerr << "Time elapsed: " << clock() - start << " ms!\n";
return 0;
}
