Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

const INF = 1 << 60

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N := sc.nextInt()
	G := make([][]int, N)
	for i := 0; i < N; i++ {
		G[i] = make([]int, N)
		for j := 0; j < N; j++ {
			G[i][j] = sc.nextInt()
		}
	}
	d := make([]int, N)
	for i := 0; i < N; i++ {
		d[i] = INF
	}
	seen := make([]bool, N)
	d[0] = 0
	ans := 0
	for {
		cur := 0
		minCost := INF
		for i := 0; i < N; i++ {
			if !seen[i] && d[i] < minCost {
				minCost = d[i]
				cur = i
			}
		}
		if minCost == INF {
			break
		}
		seen[cur] = true
		ans += d[cur]
		for i := 0; i < N; i++ {
			cost := G[cur][i]
			if cost != -1 && cost < d[i] {
				d[i] = cost
			}
		}
	}

	fmt.Fprintln(wtr, ans)
	wtr.Flush()
}

C++: #include<iostream>
#include<algorithm>

using namespace std;

#define INF 2001
#define NIL -2


struct node{
    int key=INF, pi=NIL, flag=0;
};

node grf[101];
int hv[101][101], n;

void search(){
    int min = INF, mini = NIL;
    for(int i=0;i<n;++i){
        if(grf[i].flag != 1 && grf[i].key < min){
            min = grf[i].key;
            mini= i;
        }
    }
    
    if(min == INF){
        return;
    }
    
    grf[mini].flag = 1;
    for(int j=0;j<n;++j){
        if((grf[j].flag != 1 && hv[mini][j] != -1) && hv[mini][j] < grf[j].key){
            grf[j].key = hv[mini][j];
            grf[j].pi = mini;
        }
    }
    
    return;
    
}

int main(){
    int total=0;
    cin >> n;
    for(int i=0;i<n;++i){
        for(int j=0;j<n;++j){
            cin >> hv[i][j];
        }
    }
    
    grf[0].key = 0;
    grf[0].flag = 1;
    for(int j=0;j<n;++j){
        if(hv[0][j] != -1 && hv[0][j] < grf[j].key){
            grf[j].key = hv[0][j];
            grf[j].pi = 0;
        }
    }
    
    for(int i=1;i<n;++i){
        search();
    }
    
    for(int i=0;i<n;++i){
        total+=grf[i].key;
    }
    
    cout << total << endl;
    
    return 0;
}

C++: #include <iostream>
#include <queue>
#include <utility>
using namespace std;

int a[100][100];
bool r[100];


int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin>>n;
    for(int i=0; i<n; i++) {
        for(int j=0; j<n; j++) {
            cin>>a[i][j];
        }
    }
    priority_queue<pair<int,int>, vector<pair<int,int> >, greater<pair<int,int> > >q;
    q.push(make_pair(0,0));
    int cost=0;
    pair<int,int> e;
    while(!q.empty()) {
        e=q.top();
        q.pop();
        if(r[e.second]) continue;
        r[e.second]=true;
        cost+=e.first;
        for(int i=0; i<n; i++) {
            if(a[e.second][i]!=-1) q.push(make_pair(a[e.second][i], i));
        }
    }
    cout<<cost<<'\n';
    return 0;
}

C++: #include<iostream>
#include<cstdio>

using namespace std;

#define N 101

int main(){

  int n;

  int g[N][N];
  int min=3000;
  int weight[N];
  int sum=0;

  //load n
  cin >>n;

  //load data
  for(int i=1;i<=n;i++){
    weight[i]=0;
    for(int j=1;j<=n;j++){
      scanf("%d",&g[i][j]);
    }
  }

  for(int i=1;i<=n;i++){
    for(int j=1;j<=n;j++){
      if(g[i][j]!= -1 && g[i][j]<min) {
	min=g[i][j];
      }
	weight[i]=min;
    }
  }

  for(int i=1;i<=n;i++){
    if(weight[i]!=3000) sum+=weight[i];
  }
  //print
  cout <<sum<<endl;

  return 0;

}

C++: #include<iostream>
#include<cstdio>
#include<climits>
using namespace std;

#define N 120
int n;

int g[N][N];
int mini;
int weight[N];
bool us[N];

int prim(){
  int v;
  int ans=0;
  weight[1]=0;
  
  while(true){
    v=-1;
   
    for(int i=1;i<=n;i++){
      if(us[i]!=true && (v==-1 ||weight[i]<weight[v]))v=i;
    }

    if(v==-1)break;
    us[v]=true;
    ans+=weight[v];

    for(int i=1;i<=n;i++){
      if(weight[i]>g[v][i])weight[i]=g[v][i];
      else weight[i]=weight[i];
    }
  }
  return ans;
}


int main(){

  //load n
  cin >>n;

  //load data
  for(int i=1;i<=n;i++){
    weight[i]=INT_MAX;
    us[i]=false;
    for(int j=1;j<=n;j++){
      scanf("%d",&g[i][j]);
      if(g[i][j]== -1)g[i][j]=INT_MAX;
      //    cout <<g[i][j]<<" ";
    }
    //    cout <<endl;
  }




  //print
  cout <<prim()<<endl;

  return 0;

}

C++: #include <iostream>
using namespace std;
static const int MAX = 100;
static const int INTFY = (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]=INTFY;
        p[i]=-1;
        color[i]=WHITE;
    }
    
    d[0]=0;
    
    while(1){
        minv=INTFY;
        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] != INTFY){
                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]];
    }
    return sum;
}
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) ? INTFY : e;
        }
    }
    
    cout << prim() << endl;
    return 0;
}