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#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <cmath>
#include <cassert>
#include <cstring>
#include <ext/numeric>
using namespace std ;
using namespace __gnu_cxx ;
typedef long long LL ;
typedef pair<int,int> PII ;
typedef vector<int> VI ;
const int INF = 1000*1000*1000 ;
const LL INFLL = (LL)INF * (LL)INF ;
#define REP(i,n) for(i=0;i<(n);++i)
#define ALL(c) c.begin(),c.end()
#define VAR(v,i) __typeof(i) v=(i)
#define FOREACH(i,c) for(VAR(i,(c).begin());i!=(c).end();++i)
#define CLEAR(t) memset(t,0,sizeof(t))
#define PB push_back
#define MP make_pair
#define FI first
#define SE second

template<class T1, class T2> ostream & operator<<(ostream &s, pair<T1,T2> x) { s << "(" << x.FI << "," << x.SE << ")" ; return s ; }
template<class T> ostream & operator<<(ostream &s, const vector<T> &t) { FOREACH(it, t) s << *it << " " ; return s ; }
template<class T1, class T2> ostream & operator<<(ostream &s, const map<T1, T2> &t) { FOREACH(it, t) s << *it << " " ; return s ; }

const int MAXN = 2100 ;

vector<pair<int, PII> > cand ;

set<int> S[MAXN] ;
int where[MAXN] ;

void join(int a, int b) {
	if(S[a].size() > S[b].size())
		swap(a,b) ;
	
	FOREACH(it, S[a])
		where[*it]=b ;
	S[b].insert(ALL(S[a])) ;
	S[a].clear() ;
}

int main()
{
	ios_base::sync_with_stdio(0) ;
	int n, i, j, c ;
	cin >> n ;
	for(i=1 ; i<=n ; i++)
		for(j=i ; j<=n ; j++) {
			cin >> c ;
			cand.PB(MP(c, MP(i,j))) ;
		}
	sort(ALL(cand)) ;
	
	for(i=1 ; i<=n+1 ; i++) {
		where[i] = i ;
		S[i].insert(i) ;
	}
	
	LL ret=0 ;
	FOREACH(it, cand) {
		if(where[it->SE.FI]==where[it->SE.SE+1])
			continue ;
		
		ret += it->FI ;
		join(where[it->SE.FI], where[it->SE.SE+1]) ;
	}
	cout << ret << endl ;
}