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#include <stdio.h>
#include <set>
#include <vector>

int tab[2002][2002];
const int INF = 2000000000;
int wagi[2002];


struct Cmp
{
    bool operator()(int a, int b) const
    {
        return wagi[a] < wagi[b] || wagi[a] == wagi[b] && a < b;
    }
};

int main()
{
    int N, val;
    scanf("%d\n", &N);
    
    for(int i = 0 ; i < N ; ++i)
    {
        for(int j = i + 1 ; j <= N ; ++j)
        {
            scanf("%d", &tab[i][j]);
            tab[j][i] = tab[i][j];
        }
    }

    for(int i = 0 ; i <= N ; ++i)
    {
        tab[i][i] = INF;
        wagi[i] = INF;
    }

    long long int result = 0;
    std::vector<bool> odwiedzone(N+1);
    odwiedzone[0] = true;
    std::multiset<int, Cmp> S;
    wagi[0] = 0;
    S.insert(0);

    while(!S.empty())
    {
        int s = *S.begin();
        S.erase(*S.begin());
        odwiedzone[s] = true;
        
        result += wagi[s];

        for(int i = 0 ; i <= N ; ++i)
        {
            if(!odwiedzone[i])
            {
                if(wagi[i] > tab[s][i])
                {
                    S.erase(i);
                    wagi[i] = tab[s][i];
                    S.insert(i);
                }
            }
        }
    }

    printf("%lld\n", result);
    
    return 0;
}