#define _USE_MATH_DEFINES
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <clocale>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

#define IOS ios::sync_with_stdio(false); cin.tie(0);
#define FOR(i, s, n) for(int i = (s), i##_len=(n); i < i##_len; ++i)
#define FORS(i, s, n) for(int i = (s), i##_len=(n); i <= i##_len; ++i)
#define VFOR(i, s, n) for(int i = (s); i < (n); ++i)
#define VFORS(i, s, n) for(int i = (s); i <= (n); ++i)
#define REP(i, n) FOR(i, 0, n)
#define REPS(i, n) FORS(i, 0, n)
#define VREP(i, n) VFOR(i, 0, n)
#define VREPS(i, n) VFORS(i, 0, n)
#define RFOR(i, s, n) for(int i = (s), i##_len=(n); i >= i##_len; --i)
#define RFORS(i, s, n) for(int i = (s), i##_len=(n); i > i##_len; --i)
#define RREP(i, n) RFOR(i, n, 0)
#define RREPS(i, n) RFORS(i, n, 0)
#define ALL(v) (v).begin(), (v).end()
#define SORT(v) sort(ALL(v))
#define RSORT(v) sort(ALL(v), greater<decltype(v[0])>())
#define SZ(x) ((int)(x).size())
#define PB push_back
#define MP make_pair
#define MT make_tuple
#define BIT(n) (1LL<<(n))
#define UNIQUE(v) v.erase(unique(ALL(v)), v.end())

using ll = long long;
using Pi_i = pair<int, int>;
using VB = vector<bool>;
using VC = vector<char>;
using VD = vector<double>;
using VI = vector<int>;
using VLL = vector<ll>;
using VS = vector<string>;
using VSH = vector<short>;

const int MOD = 1000000007;
const int INF = 1000000000;
const int NIL = -1;

template<class T, class S>
bool chmax(T &a, const S &b){
    if(a < b){
        a = b; return true;
    }
    return false;
}
template<class T, class S>
bool chmin(T &a, const S &b){
    if(b < a){
        a = b; return true;
    }
    return false;
}

/*　O(V log E) 
#include <algorithm>
#include <queue>
#include <vector>
#define FOR(i, s, n) for(int i = s, i##_len=(n); i < i##_len; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(v) (v).begin(), (v).end()
const int INF = 1000000000;
using namespace std;
using ll = long long;
using Pi_i = pair<int, int>;
*/

struct edge{
    int to, cost;
    edge(int To, int Cost): to(To), cost(Cost){};
};


int V; //頂点数
vector<vector<edge>> G;
vector<int> d; //既に木に含まれる点からの距離

int prim(){
    int res = 0;
    //Pi_i first: 距離　second: 頂点
    priority_queue<Pi_i, vector<Pi_i>, greater<Pi_i>> que;
    fill(ALL(d), INF);
    d[0] = 0;
    que.push(MP(0, 0));

    while(!que.empty()){
        Pi_i p = que.top(); que.pop();
        int v = p.second;
        if(d[v] < p.first) continue;
        d[v] = 0;
        res += p.first;
        for(edge &e : G[v]){
            if(d[e.to] > e.cost){
                d[e.to] = e.cost;
                que.push(MP(d[e.to], e.to));
            }
        }
    }
    return res;
}

int main(){
    cin >> V;
    G.resize(V);
    d.resize(V);
    REP(i, V){
        REP(j, V){
            int cst; cin >> cst;
            if(cst != -1){
                G[i].PB(edge(j, cst));
                G[j].PB(edge(i, cst));
            }
        }
    }
    cout << prim() << endl;
    return 0;
}




Measured memory_bytes: 3244