Go: package main

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

// Define disjoint-set forests

type vertexNo int

type vertex struct {
	number vertexNo
	rank int
	parent *vertex
}

func makeSet(number vertexNo) vertex {
	return vertex {
		number: number,
		rank: 0,
		parent: nil,
	}
}

func union(x, y *vertex) *vertex {
	return link(findSet(x), findSet(y))
}

func link(x, y *vertex) *vertex {
	if x.rank > y.rank {
		y.parent = x
		return x
	} else {
		x.parent = y
		if x.rank == y.rank {
			y.rank += 1
		}
		return y
	}
}

func findSet(v *vertex) *vertex {
	if v.parent == nil {
		return v
	}
	v.parent = findSet(v.parent)
	return v.parent
}

// Function to calculate minimum spanning tree

type matrix [][]int

type edge struct {
	one vertexNo
	two vertexNo
	weight int
}

const(
	MAX_VERTICES = 100
)

func newEdgesFromMatrix(matrix matrix) []edge {
	edges := make([]edge, 0, MAX_VERTICES * MAX_VERTICES)

	for i := 0; i < len(matrix); i++ {
		row := matrix[i]
		for j := i; j < len(row); j++ {
			if row[j] >= 0 {
				edge := edge{one: vertexNo(i+1), two: vertexNo(j+1), weight: row[j]}
				edges = append(edges, edge)
			}
		}
	}

	return edges
}

func solve(matrix matrix) int {
	nVertices := len(matrix)

	// initialize vertices
	vertices := make([]vertex, nVertices)
	for i := 0; i < nVertices; i++ {
		vertices[i] = makeSet(vertexNo(i+1))
	}

	// prepare edges sorted in the ascending order of weight
	edges := newEdgesFromMatrix(matrix)
	sort.Slice(edges, func(i, j int) bool {
		return edges[i].weight < edges[j].weight
	})

	unionCount := 0
	weightSum := 0
	for unionCount < nVertices-1 {
		for i := 0; i < len(edges); i++ {
			edge := edges[i]
			v1 := &vertices[edge.one-1]
			v2 := &vertices[edge.two-1]
			rep1 := findSet(v1)
			rep2 := findSet(v2)
			if rep1.number == rep2.number {
				continue
			}
			union(rep1, rep2)
			edges = append(edges[0:i], edges[i+1:]...)
			weightSum += edge.weight
			unionCount++
			break
		}
	}

	return weightSum
}

// main

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}

	matrix := parseMatrix(n, sc)

	edges := newEdgesFromMatrix(matrix)
	sort.Slice(edges, func(i, j int) bool {
		return edges[i].weight < edges[j].weight
	})

	fmt.Println(solve(matrix))
}

func parseMatrix(n int, sc *bufio.Scanner) [][]int {
	matrix := make([][]int, n)
	for i := 0; i < n; i++ {
		matrix[i] = make([]int, n)
		for j := 0; j < n; j++ {
			x, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			matrix[i][j] = x
		}
	}
	return matrix
}

func nextText(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

func nextInt(sc *bufio.Scanner) (int, error) {
	return strconv.Atoi(nextText(sc))
}

C++: #include "bits/stdc++.h"

#define REP(i,num) for(int i=0;i<(num);++i)
#define ALL(c) c.begin(),c.end()
#define PRINTALL(c) for(auto& x:c){cout<<x<<' ';}cout<<endl;
#define PAIRCOMP(c,comp) [](const pair<ll,ll>& lhs,const pair<ll,ll>& rhs){return lhs.c comp rhs.c;}

using namespace std;
using ll = long long;

constexpr ll atcoder_mod = 1e9+7;

template<typename T=int>
T in(){T x; cin >> x; return (x);}
template<typename T=int,typename C=vector<T>>
C vecin(int N){C x(N);REP(i,N){x[i]=in<T>();}return move(x);}

void vout(){cout << endl;}
template<typename Head,typename... Tail>
void vout(Head&& h,Tail&&... t){cout << ' ' << h;vout(forward<Tail>(t)...);}
void out(){cout << endl;}
template<typename Head,typename... Tail>
void out(Head&& h,Tail&&... t){cout << h;vout(forward<Tail>(t)...);}

class Edge{
public:
	ll to,weight;
	bool use{true};
	Edge(ll t,ll w):to(t),weight(w){}
};

class Edge2{
public:
	ll from,to,weight;
	Edge2()=default;
	Edge2(ll f,ll t,ll w):from(f),to(t),weight(w){}
};

class ConnectNodeInfo{
	vector<vector<Edge>> graph;
public:
	ConnectNodeInfo(int node_num){
		graph.resize(node_num);
	}
	void AddNonDirectionalConnection(ll u,ll v,ll w){
		graph[u].emplace_back(v,w);
		graph[v].emplace_back(u,w);
	}
	void AddDirectionalConnection(ll u,ll v,ll w){
		graph[u].emplace_back(v,w);
	}
	vector<Edge>& operator[](ll index){
		return graph[index];
	}
	size_t size(){return graph.size();}
};

class SearchPath{
	set<ll> visit;

	bool CanReachImpl(int start,int end,ConnectNodeInfo& connect){
		bool reach=false;
		if(start==end) return true;

		for(int i=0,ei=connect[start].size();i<ei;i++){
			if(!connect[start][i].use) continue;
			auto res = visit.emplace(connect[start][i].to);
			if(!res.second) continue;
			reach |= CanReachImpl(connect[start][i].to,end,connect);
		}
		return reach;
	}
public:
	bool CanReach(int start,int end,ConnectNodeInfo& connect){
		visit.clear();
		visit.emplace(start);
		return CanReachImpl(start,end,connect);
	}
};

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);

	int N=in();
	vector<vector<int>> C(N,vector<int>(N));
	ConnectNodeInfo connect(N);
	vector<Edge2> edge;
	REP(i,N){
		REP(j,N){
			C[i][j]=in();
		}
	}
	REP(i,N){
		for(int j=i;j<N;j++){
			int v=C[i][j];
			if(v!=-1){
				connect.AddNonDirectionalConnection(i,j,v);
				edge.emplace_back(i,j,v);
			}
		}
	}
	sort(ALL(edge),[](Edge2& l,Edge2& r){return l.weight>r.weight;});
	SearchPath sp;
	int M=edge.size();
	ll sum=0;
	REP(i,M){
		auto& e=edge[i];
		for(auto& x:connect[e.from]){
			if(x.to==e.to) x.use=false;
		}
		for(auto& x:connect[e.to]){
			if(x.to==e.from) x.use=false;
		}
		if(!sp.CanReach(e.from,e.to,connect)){
			for(auto& x:connect[e.from]){
				if(x.to==e.to) x.use=true;
			}
			for(auto& x:connect[e.to]){
				if(x.to==e.from) x.use=true;
			}
			sum+=e.weight;
		}
	}
	
	out(sum);
	return 0;
}