#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define pb(e) push_back(e)
#define sv(a) sort(a.begin(),a.end())
#define sa(a,n) sort(a,a+n)
#define mp(a,b) make_pair(a,b)
#define vf first
#define vs second
#define ar array
#define all(x) x.begin(),x.end()
const int inf = 0x3f3f3f3f;
const int mod = 1000000007;
const double PI=3.14159265358979323846264338327950288419716939937510582097494459230;
bool remender(ll a , ll b){return a%b;}
const int N = 51;
int dp[N][N][N][N];
int p[N][N];
int cal(int x1 , int y1 , int x2 , int y2){
return p[x2][y2] - (x1 > 0 ? p[x1-1][y2] : 0) - (y1 > 0 ? p[x2][y1-1] : 0) + (x1 > 0 && y1 >0 ? p[x1-1][y1-1] : 0);
}
int rec(int x, int y , int x1 , int y1){
if(x == x1 && y == y1)return 0;
if(dp[x][y][x1][y1] != -1)return dp[x][y][x1][y1];
int res = INT_MAX;
for(int i = x; i < x1; i++){
res = min(res , rec(x,y,i,y1) + rec(i + 1 , y , x1 , y1));
}
for(int j = y; j < y1; j++){
res = min(res , rec(x,y,x1,j) + rec(x,j + 1 , x1 , y1));
}
return dp[x][y][x1][y1] = res + cal(x,y,x1,y1);
}
void solve(){
int n , m;
cin >> n >> m;
int arr[n][m];
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++){
cin >> arr[i][j];
}
}
for(int i = 0; i < n; i++){
p[i][0] = arr[i][0];
for(int j = 1; j < m; j++)p[i][j] = p[i][j-1] + arr[i][j];
}
for(int j = 0; j < m; j++){
for(int i = 1; i < n; i++){
p[i][j] += p[i-1][j];
}
}
memset(dp,-1,sizeof dp);
cout << rec(0,0,n-1,m-1) << '\n';
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
//int t;cin >> t;while(t--)
solve();
return 0;
}
