Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func main() {
	fp := os.Stdin
	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(os.Stdout)

	n := getNextInt(scanner)

	g := make([][]int, n)
	ans := make([][]int, n)

	inf := 1 << 30
	for i := 0; i < n; i++ {
		g[i] = make([]int, n)
		ans[i] = make([]int, n)
		for ii := 0; ii < n; ii++ {
			g[i][ii] = getNextInt(scanner)
			if g[i][ii] == -1 {
				g[i][ii] = inf
			}
			ans[i][ii] = -1
		}
	}

	im := make(IntMap, 1)

	im.increment(1)

	for len(im) < n {
		min := inf
		u := -1
		v := -1
		for i := range im {
			for ii := 0; ii < n; ii++ {
				if im.get(ii) != 0 {
					continue
				}
				if min > g[i][ii] {
					min = g[i][ii]
					u = i
					v = ii
				}
			}
		}
		im.increment(v)
		ans[u][v] = min
		ans[v][u] = min
	}

	sum := 0
	for i := 0; i < n-1; i++ {
		for ii := i + 1; ii < n; ii++ {
			if ans[i][ii] != -1 {
				sum += ans[i][ii]
			}
		}
	}

	fmt.Fprintln(writer, sum)
	writer.Flush()
}

// IntMap ...
type IntMap map[int]int

func (m IntMap) get(key int) int {
	if _, ok := m[key]; ok {
		return m[key]
	}
	return 0
}
func (m IntMap) increment(key int) {
	if _, ok := m[key]; ok == false {
		m[key] = 0
	}
	m[key]++
}

C++: #include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdint.h>
#include <tuple>
#include <utility>
#include <vector>

using namespace std;

typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
static const double EPS = 1e-12;
static const double PI = acos(-1.0);

#define FOR(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define REP(i, n) for (int i = 0; i < (int)(n); i++)
#define ALL(a) (a).begin(), (a).end()
#define DEBUG(x) cout << #x << ": " << x << endl

static const ll INF = std::numeric_limits<ll>::max() / 3;
static const ll MAX_V = 100;  // TODO

ll cost[MAX_V][MAX_V];  // TODO
ll mincost[MAX_V];
bool used[MAX_V];
ll V;  // TODO

typedef pair<ll, ll> Node;

int prim() {
  priority_queue<Node, vector<Node>, greater<Node>> q;
  q.push(Node{0, 0});
  ll res = 0;
  while (!q.empty()) {
    Node node = q.top();
    q.pop();
    if (used[node.second]) {
      continue;
    }
    used[node.second] = true;
    res += node.first;
    for (ll u = 0; u < V; u++) {
      if (cost[node.second][u] != INF) {
        q.push(Node{cost[node.second][u], u});
      }
    }
  }
  return res;
}

void solve(long long n, vector<vector<long long>> a) {
  V = n;
  REP(i, n) {
    REP(j, n) {
      if (a[i][j] == -1) {
        cost[i][j] = INF;
      } else {
        cost[i][j] = a[i][j];
      }
    }
  }
  std::cout << prim() << std::endl;
}

int main() {
  long long n;
  scanf("%lld", &n);
  vector<vector<long long>> a(n, vector<ll>(n));
  REP(i, n) {
    REP(j, n) {
      scanf("%lld", &a[i][j]);
    }
  }
  solve(n, std::move(a));
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define vv(type, c, m, n, i) vector<vector<type>> c(m, vector<type>(n, i));
#define rep(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)
#define rrep(i,a,n) for(int i=(a), i##_len=(n); i>i##_len; --i)
#define len(x) ((int)(x).size())
#define mp make_pair
#define eb emplace_back
typedef long long ll;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long long> vll;
typedef vector<string> vs;
typedef vector<bool> vb;
constexpr int MAX = 101;
constexpr int INF = 1<<21;
enum Color { WHITE = 0, GRAY, BLACK };
int n;
vv(int, M, MAX, MAX, INF);
inline int prim() {
	vi d(n, INF), t(n, -1), color(n, WHITE);
	d[0] = 0;
	int minv, u;
	while(true) {
		minv = INF;
		u = -1;
		rep(i, 0, n) {
			if(minv > d[i] && color[i] != BLACK) {
				u = i;
				minv = d[i];
			}
		}
		if(u == -1) break;
		color[u] = BLACK;
		rep(v, 0, n) {
			if(color[v] != BLACK && d[v] > M[u][v]) {
				d[v] = M[u][v];
				t[v] = u;
				color[v] = GRAY;
			}
		}
	}
	return accumulate(all(d), 0);
;
}
int main() {
	cin >> n;
	int e;
	rep(i, 0, n) {
		rep(j, 0, n) {
			cin >> e;
			if(e != -1) M[i][j] = e;
		}
	}
	P(prim());
	return 0;
}

C++: #include<iostream>
using namespace std;
static const int MAX = 100;
static const int INFTY = (1 << 21);
static const int WHITE = 0;
static const int GRAY = 1;
static const int BLACK = 2;

int n, M[MAX][MAX];

int prim() {
	int u, minv;
	int d[MAX], p[MAX], color[MAX];
	
	for(int i = 0; i < n; i++) {
		d[i] = INFTY;
		p[i] = -1;
		color[i] = WHITE;
	}
	
	d[0] = 0;
	
	while(1) {
		minv = INFTY;
		u = -1;
		for(int i = 0; i < n; i++) {
			if(minv > d[i] && color[i] != BLACK) {
				u = i;
				minv = d[i];
			}
		}
	   if(u == -1) break;
	   color[u] = BLACK;
	   for(int v = 0; v < n; v++) {
           if(color[v] != BLACK && M[u][v] != INFTY){
		   	  if(d[v] > M[u][v]) {
	   		      d[v] = M[u][v];
   		          p[v] = u;
           	   	  color[v] = GRAY;
   	           }
           }
   	   }	
	}
	int sum = 0; 
	for(int i = 0; i < n; i++) {
		if(p[i] != -1) sum += M[i][p[i]];
	}
} 

int main() {
	cin >> n;
	
	for(int i = 0; i < n; i++) {
		for(int i = 0; i < n; i++){
			int e;
			cin >> e;
			M[i][j] = (e == -1) ? INFTY :e;
		}
	}
	
	cout << prim();
	
	return 0;
}

C++: #include<iostream>
using namespace std;
static const int MAX = 100;
static const int INFTY = (1 << 21);
static const int WHITE = 0;
static const int GRAY = 1;
static const int BLACK = 2;

int n, M[MAX][MAX];

int prim() {
	int u, minv;
	int d[MAX], p[MAX], color[MAX];
	
	for(int i = 0; i < n; i++) {
		d[i] = INFTY;
		p[i] = -1;
		color[i] = WHITE;
	}
	
	d[0] = 0;
	
	while(1) {
		minv = INFTY;
		u = -1;
		for(int i = 0; i < n; i++) {
			if(minv > d[i] && color[i] != BLACK) {
				u = i;
				minv = d[i];
			}
		}
	   if(u == -1) break;
	   color[u] = BLACK;
	   for(int v = 0; v < n; v++) {
           if(color[v] != BLACK && M[u][v] != INFTY){
		   	  if(d[v] > M[u][v]) {
	   		      d[v] = M[u][v];
   		          p[v] = u;
           	   	  color[v] = GRAY;
   	           }
           }
   	   }	
	}
	int sum = 0; 
	for(int i = 0; i < n; i++) {
		if(p[i] != -1) sum += M[i][p[i]];
	}
} 

int main() {
	cin >> n;
	
	for(int i = 0; i < n; i++) {
		for(int j = 0; j < n; j++){
			int e;
			cin >> e;
			M[i][j] = (e == -1) ? INFTY :e;
		}
	}
	
	cout << prim();
	
	return 0;
}