#include<bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,avx2,bmi,bmi2,popcnt,lzcnt")
const int MOD = 1e9+7;
using namespace std;
void solve(){
int n, m;
cin >> n >> m;
int dp[n][m][n][m];
int pr[n][m];
for(int i = 0;i < n;i++) for(int j = 0;j < m;j++) {
cin >> pr[i][j];
dp[0][0][i][j] = 0;
if(i) pr[i][j] += pr[i-1][j];
if(j) {
pr[i][j] += pr[i][j-1];
if(i) pr[i][j] -= pr[i-1][j-1];
}
}
for(int h = 0;h < n;h++){
for(int w = h ? 0 : 1;w < m;w++){
for(int i = 0;i+h < n;i++){
for(int j = 0;j+w < m;j++){
dp[h][w][i][j] = pr[i+h][j+w]-(i ? pr[i-1][j+w] : 0)-(j ? pr[i+h][j-1] : 0)+(i&&j ? pr[i-1][j-1] : 0);
int x = INT_MAX;
for(int k = 0;k < h;k++) x = min(x, dp[k][w][i][j]+dp[h-k-1][w][i+k+1][j]);
for(int k = 0;k < w;k++) x = min(x, dp[h][k][i][j]+dp[h][w-k-1][i][j+k+1]);
dp[h][w][i][j] += x;
}
}
}
}
cout << dp[n-1][m-1][0][0] << '\n';
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
solve();
}
