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#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#define MP make_pair
#define f first
#define s second

using namespace std;


int tab[3000];
vector < pair < int, pair<int, int> > > V;
int FIND(int x){

    if(x==tab[x] ) return x;
    tab[x]=tab[FIND(tab[x])];
    return tab[x];
}   
     
void UNION(int a, int b){
     if (FIND(a)!=FIND(b)) tab[FIND(a)]=FIND(b);
     return ;
     }

int main()
{
	//ios_base::sync_with_stdio(0);
	int n, pom, skladowe;
	//cin>>n;
	scanf("%d", &n);
    skladowe = n+1;
	for(int i=1; i<=n+1; i++)
		tab[i]=i;
	for(int i=1; i<=n; i++)
		for(int j=i+1; j<=n+1; j++)
		{
            scanf("%d", &pom);
			//cin>>pom;
			V.push_back(MP(pom, MP(i, j)));
		}
	sort(V.begin(), V.end());
	long long koszt=0, k;
	for(int i=0; skladowe>1; i++)
	{
		if (FIND(V[i].s.f) != FIND(V[i].s.s))
		{
			skladowe--;
			k=V[i].f;
			koszt+=k;
			UNION(V[i].s.f, V[i].s.s);
		}
	}
	cout<<koszt;
//	system("PAUSE");
	return 0;
}
/*
5
1 2 3 4 5
4 3 2 1
3 4 5 
2 1
5

6
1 7 2 7 8 10
9 3 4 11 7
4 8 9 13
9 6 10
11 5
13
*/