#include <iostream>
#include<fstream>
#include<vector>
#include<algorithm>
using namespace std;

ifstream fin("oracol.in");
ofstream fout("oracol.out");

const int N_MAX = 2e5 + 5;
struct ura {
    int x, y, c;
    bool operator<(const ura &other)const {
        return c<other.c;
    };
};
int n, m;

int t[N_MAX], p[N_MAX];

vector<ura>v, r;

int tata(int nodd) {
    if(nodd==t[nodd])
        return nodd;
    return t[nodd]=tata(t[nodd]);
}

void tacpac(int x, int y) {
    x=tata(x);
    y=tata(y);
    if(p[x]==p[y]) {
        p[x]++;
        t[y]=x;
    }
    else
        if(p[x]>p[y])
            t[y]=x;
        else
            t[x]=y;
}
int main() {
      fin>>n;
    for(int i=1; i<=1000; i++) {
        t[i]=i;
    }
    for(int i=1; i<=n; i++) {
            for(int j=i;j<=n;j++) {
                    int c;
        fin>>c;
        v.push_back({i-1, j, c});
    }
    }


    sort(v.begin(), v.end());
     long long coost=0;
    for(auto it : v) {
        if(tata(it.x)!=tata(it.y)) {
            tacpac(it.x, it.y);
            coost+=it.c;
            r.push_back(it);
        }
    }
    fout<<coost;

    return 0;
}