#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
typedef long long ll;
const int MAX = 52;
const int INF = 0x3f3f3f3f;
int n, m, p[MAX][MAX], ps[MAX][MAX], dp[MAX][MAX][MAX][MAX];
int getCost(int x1, int y1, int x2, int y2){
return ps[x2][y2] - ps[x1 - 1][y2] - ps[x2][y1 - 1] + ps[x1 - 1][y1 - 1];
}
int solve(int x1, int y1, int x2, int y2){
if(x1 == x2 && y1 == y2) return 0;
if(dp[x1][y1][x2][y2] != -1) return dp[x1][y1][x2][y2];
int resp = INF;
for(int i = x1; i < x2; i++)
resp = min(resp, solve(x1, y1, i, y2) + solve(i + 1, y1, x2, y2));
for(int i = y1; i < y2; i++)
resp = min(resp, solve(x1, y1, x2, i) + solve(x1, i + 1, x2, y2));
return dp[x1][y1][x2][y2] = resp + getCost(x1, y1, x2, y2);
}
int32_t main(void){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> m;
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
cin >> p[i][j];
ps[i][j] = ps[i - 1][j] + ps[i][j - 1] - ps[i - 1][j - 1] + p[i][j];
}
}
memset(dp, -1, sizeof(dp));
cout << solve(1, 1, n, m) << '\n';
}
