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// Artur Kraska, II UWr

#include <algorithm>
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <vector>
#include <cmath>
#include <list>
#include <set>
#include <map>

#define forr(i, n)                  for(int i=0; i<n; i++)
#define FOREACH(iter, coll)         for(typeof(coll.begin()) iter = coll.begin(); iter != coll.end(); ++iter)
#define FOREACHR(iter, coll)        for(typeof(coll.rbegin()) iter = coll.rbegin(); iter != coll.rend(); ++iter)
#define lbound(P,R,PRED)            ({typeof(P) X=P,RRR=(R), PPP = P; while(PPP<RRR) {X = (PPP+(RRR-PPP)/2); if(PRED) RRR = X; else PPP = X+1;} PPP;})
#define testy()                     int _tests; scanf("%d", &_tests); FOR(_test, 1, _tests)
#define CLEAR(tab)                  memset(tab, 0, sizeof(tab))
#define CONTAIN(el, coll)           (coll.find(el) != coll.end())
#define FOR(i, a, b)                for(int i=a; i<=b; i++)
#define FORD(i, a, b)               for(int i=a; i>=b; i--)
#define MP                          make_pair
#define PB                          push_back

#define M 1000000007
#define INF 1000000007

using namespace std;

int n, a, b, ile;

struct fu
{
    int o;
    int ile;
};
fu tab[2007];

struct przedzial
{
    int p, k;
    int koszt;
};
przedzial t[5000007];

static inline bool comp(const przedzial &p1, const przedzial &p2)
{
    return p1.koszt < p2.koszt;
}

static inline int Find(int nr)
{
    if(tab[nr].o == nr)
        return nr;
    tab[nr].o = Find(tab[nr].o);
    return tab[nr].o;
}

static inline bool Union(int a, int b)
{
    a = Find(a);
    b = Find(b);
    if(a != b)
    {
        if(tab[a].ile < tab[b].ile)
        {
            tab[b].o = a;
            tab[a].ile += tab[b].ile+1;
        }
        else
        {
            tab[a].o = b;
            tab[b].ile += tab[a].ile+1;
        }
        return 1;
    }
    return 0;
}

int main()
{
    scanf("%d", &n);
    forr(i, n)
    {
        FOR(j, i+1, n)
        {
            scanf("%d", &t[ile].koszt);
            t[ile].p = i;
            t[ile].k = j;
            ile++;
        }
    }

    sort(t, t+ile, comp);

    forr(i, n+1)
        tab[i].o = i;

    long long wynik = 0;

    forr(i, ile)
    {
        if(Union(t[i].p, t[i].k))
            wynik += t[i].koszt;
    }

    cout << wynik << endl;

	return 0;
}