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//Michal Wos MIM UW
#include <climits>
#include <cstdlib>
#include <iostream>
#include <stdio.h>
#include <vector>
#include <algorithm>
#include <set>
#include <map>
#include <cmath>
#include <string>
#include <string.h>
#define pb push_back
#define pii pair<int,int>
#define vi vector<int>
#define f first
#define s second
#define x first
#define y second
#define Size(x) ((int)(x).size())
#define FOR(z,b,e) for(__typeof(b) z = b;  z<=e; z++ )
#define debon 1
#define deb(burak) if(debon) {cout<<"DEB-> "<<#burak<<": "<<burak<<endl;}
#define debv(burak) if(debon) {cout<<"DEB-> "<<#burak<<": \t"; for(unsigned int zyx=0;zyx<burak.size();zyx++) cout<<burak[zyx]<<" "; cout<<endl;}
#define debt(burak,SIzE) if(debon) {cout<<"DEB-> "<<#burak<<": \t"; for(unsigned int zyx=0;zyx<SIzE;zyx++) cout<<burak[zyx]<<" "; cout<<endl;}
#define debend if(debon) {cout<<"_____________________"<<endl;}
#define memcheck if(debon) {FILE *fp = fopen("/proc/self/status","r");while( !feof(fp) ) putchar(fgetc(fp));}
using namespace std;
typedef unsigned long long ULL;
typedef long long LL;
void readLL(LL *n) {register char c=0; while (c < 33) c=getc_unlocked(stdin); (*n)=0; while (c>32) {(*n)=(*n)*10LL + (c-'0'); c=getc_unlocked(stdin);}}
const int inf=1073741824,mod=1e9+7;
const int s=2010;

int tab[s], ile[s];

int Find(int a)
{
	if (tab[a] == a) {
	    return a;
	}
	int fa = Find(tab[a]);
	tab[a] = fa;
    return fa;
}

bool Union(int a, int b)
{
	int fa = Find(a);
	int fb = Find(b);

	if (fa == fb) {
	    return false;
	}
	if (ile[fa] <= ile[fb]) {
		ile[fb] += ile[fa];
		tab[fa] = fb;
	}
	else {
		ile[fa] += ile[fb];
		tab[fb] = fa;
	}

    return true;
}


int main()
{
    #define edge pair<ULL, pii>
    #define waga first
    #define va second.first
    #define vb second.second
    vector <edge> E;

    int n, c;
    ULL res = 0;
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        for (int j = i; j < n; j++) {
            scanf("%d", &c);
            E.pb(edge(c,pii(i, j+1)));
        }
    }

    sort(E.begin(),E.end());

     //init F&U
	for (int i=0; i<=n; i++)
	{
		tab[i] = i;
		ile[i] = 1;
	}

    //MST
    int kr = 0;
    for (int i = 0; i < Size(E); i++) {
        if ( Find(E[i].va) != Find(E[i].vb) ) {
            Union(E[i].va, E[i].vb);
            res += E[i].waga;
            kr++;
            if ( kr == n ) {
                printf("%llu\n", res);
                return 0;
            }
        }
    }
    return 1;
}