#include <bits/stdc++.h>
#define int long long
using namespace std;
int parent[2048];
int dsu(int node) {
if(parent[node] == node) return node;
return parent[node] = dsu(parent[node]);
}
signed main(){
for(int i = 0; i < 2048; i++) parent[i]= i;
int n;
cin >> n;
int anti[n][n];
vector<pair<int, pair<int, int>>> edges;
for(int i = 0; i < n; i++) {
for(int j = 0; j < n; j++) {
cin >> anti[i][j];
edges.push_back({anti[i][j], {i, j}});
}
}
sort(edges.begin(), edges.end());
int total = 0;
int numedges[n];
for(int i = 0; i < n ; i++) numedges[i] = 0;
for(int i = 0; i < n * n; i++) {
if(numedges[edges[i].second.first] < 2 && numedges[edges[i].second.second] < 2 && dsu(edges[i].second.first) != dsu(edges[i].second.second)) {
total += edges[i].first;
parent[dsu(edges[i].second.first)] = dsu(edges[i].second.second);
numedges[edges[i].second.first]++;
numedges[edges[i].second.second]++;
}
}
cout<<total<<'\n';
return 0;
}
