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++: ////////////////////////////////////////
//ALDS1_12_A:   Minimum Spanning Tree
//????????§??????????????±??£?????????????§£(?´?????????????????§????)??????????????¢??°?????£????????????????????????
////////////////////////////////////////

#include <iostream>
#include <algorithm> // next_permutation
#include <iomanip>
#include <cmath>
#include <vector>
#include <sstream>
#include <string>
#include <cstdio>
#include <stack>
#include <queue>
#include <list>
#include <numeric> //accumulate
//#include <unordered_map> //???????????\??¢??°
#include <fstream> //ifstream, ofstream

//#define NDEBUG //NDEBUG???#include <cassert>???????????????????????????????????´???assert?????????????????????????????????NDEBUG?????????????????????????????????????????????
#include <cassert> //assert


using namespace std;

//???????????°??????TEST????????????????????¬???????????????????????????????????¢????????????
#define TEST //*******************************************************************************************************************************************
//?????????????????¨??§?????\????????????????????????????????°?????????????¨???????????????????dout???????????????????????§???????????¬??????????????????????????????????????????
//??????????????????????????????????????????????????????????§?CPU???????£??????????????????§???TLE?????????????????????????????????????????§????????¨???                           ????????????????????????cerr????????£????????????????????????????????????
#ifdef TEST
#define dout cout
#define din cin
#else
stringstream dummy; //???????????°??????dout?????????????????????????????????
#define dout dummy.str(""); dummy.clear(stringstream::goodbit); dummy //dummy?????????????????????????????????????????¨?????¢?????¢???????????????
//???????????¨??????????????????goodbit?????????????????????????????¨???????????´????????????????????????????????¨?????°?????????????????§???????????????????????????????????? http://d.hatena.ne.jp/linden/20060427/p1
#endif

//?¨??????????????????????????????????????????????????????´??????OUTPUTFILE????????????????????¬???????????????????????????????????¢????????????
//#define OUTPUTFILE "output.txt" //*******************************************************************************************************************************************
#ifdef OUTPUTFILE
#define dout outputfile //??¨????????????TLE????????§?????????dout?????¨??¨??????????????¢????????????????????????????????????????????§????¨????????????´??????????????£??????????????????????¨?????????????????????????????????????????????§?????????????????????
ofstream outputfile(OUTPUTFILE);
#define OutputFilePath "/Users/Nag/Documents/Prgm/Test/DerivedData/Test/Build/Products/Debug/output.txt"
#endif

//?¨??????\???????????????????????????????????????????????´??????INPUTFROMTEXTFILE????????????????????¬???????????????????????????????????¢????????????
//#define INPUTFILE "input.txt" //*******************************************************************************************************************************************
#ifdef INPUTFILE
#define din inputfile
ifstream inputfile(INPUTFILE);
#endif


#define disp(A) dout << #A << " = " << setw(3) << (A) << endl
#define disP(A) dout << setw(3) << (A) << " " // << setw(3) ??????????????\????????????
#define rep(i,a,n) for(int (i)=(a); (i)<(n); (i)++)
#define dispAll(A,n) dout << #A << " = "; rep(j, 0, (n)) {disP(A[j]);} dout << endl

typedef pair<int,int> pii;
typedef vector<int> vi;
typedef unsigned long long ll;


const int INF = 2e9-1;

#define N_MAX 100 //num of vertex
//#define M_MAX 10000 //mum of edge

int N;
int matrix[N_MAX][N_MAX];

vector< pair< int, pii >> edge;


int color[N_MAX]; //????????¨???????±?????????????vertex???????????°?????§???????????????????´?????????????????§????
#define isSame(x,y) (find(x)==find(y))
#define unite(x,y) color[find(x)] = find(y)
int find(int x) {
    if( color[x]==x ) return x;
    return color[x] = find( color[x] );
}





int main() {
    
    //read input data
    din >> N;
    rep(i,0,N) {
        rep(j,0,N) {
            din >> matrix[i][j];
        }
    }
    
    //construct edge data
    //matrix???????????????????????????????????????
    rep(i,0,N) {
        rep(j,i+1,N) {
            if( matrix[i][j] != -1)
                edge.push_back(make_pair(matrix[i][j], make_pair(i, j)));
        }
    }
    
    //??????????????±???????????????????????§??????????????????
    sort(edge.begin(), edge.end());
    
    
    //???vertex????????????????????????
    rep(i,0,N) color[i] = i;
    
    
    //??????????????????
    ll minCost = 0;
    while( !edge.empty() ) {
//        dout << "----------------------\n";
        
        auto e = edge.front(); //?????????????°???????e?????????
        
        auto cost = e.first;
        auto v1 = e.second.first; //???e?????????v1??¨v2?????\?¶?????????????
        auto v2 = e.second.second;
        
//        //test display
//        dout << "cost=" << cost << " : " << v1 << "--" << v2 << endl;
//        disp(isSame(v1, v2));
        
        
        if( !isSame(v1, v2) ) { //v1??¨v2???????????\?????°????????????????±???????????????°??????e????????¨??????v1??¨v2?????\?¶???????????????§???????????°??????????????£?????´?????????e??????????????¨???????????§????????????????????§NG
//            dout << "?????????????????¨!!\n";
            
            minCost += cost;
            unite(v1, v2);
        }
        
//        //test display
//        rep(i,0,N) {
//            disP(i); disp(color[i]);
//        }
//        disp(minCost);
        
        
            
        edge.erase(edge.begin());
    }
    
    
    
    //output
    dout << minCost << endl;
   
    
    
    
#ifdef INPUTFILE
    inputfile.close();
#endif
    
#ifdef OUTPUTFILE
    outputfile.close();
    cout << "\"" << OutputFilePath << "\"" << endl;
#endif
    
    return 0;
}