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#include<algorithm>
#include<bitset>
#include<cassert>
#include<complex>
#include<cstring>
#include<cstdio>
#include<iomanip>
#include<map>
#include<iostream>
#include<queue>
#include<set>
#include<stack>
#include<string>
#include<vector>

#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 REP(i,n) for(int i=0; i<(n); ++i)
#define VAR(v,i) __typeof(i) v = (i)
#define FORE(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)
#define ALL(x) (x).begin(),(x).end()
#define SZ(x) ((int)(x).size())
#define PB push_back
#define MP make_pair
#define X first
#define Y second
#define debug(x) { cerr << #x <<" = " << (x) << endl; }
#define debugv(x) { cerr << #x << " = "; FORE(it, x) cerr << *it << ", "; cerr << endl;  }
#define dprintf(...) fprintf(stderr, __VA_ARGS__)

using namespace std;

typedef pair<int, int> PII;;
typedef vector<int> VI;
typedef long long LL;
typedef long double LD;
template<class C> void mini(C&a4, C b4) { a4 = min(a4,b4); }
template<class C> void maxi(C&a4, C b4) { a4 = max(a4,b4); }


template<class T1, class T2> ostream& operator<<(ostream &out, pair<T1, T2> pair) { return out << "(" << pair.X << ", "<< pair.Y << ")"; };

struct E {
    int u, v;
    int c;
};

bool cmp(const E& a, const E& b) {
    return a.c < b.c;
}

const int N = 2005;
E edges[N*N];
int parent[N];

int find(int u) {
    if (parent[u] == u) return u;
    return parent[u] = find(parent[u]);
}

void unionn(int u, int v) {
    parent[find(u)] = find(v);
}

int main() {
    ios_base::sync_with_stdio();
    cout << fixed << setprecision(10);
   
    int k = 0;
    int n; scanf("%d", &n);
    FOR(i, 0, n-1) FOR(j, i+1, n) {
        edges[k].u = i;
        edges[k].v = j;
        scanf("%d", &edges[k++].c);
    }
   
    sort(edges, edges+k, cmp);
    REP(i, n+1) parent[i] = i;

    LL sum = 0;
    for(E& e: edges) {
        if (find(e.u) == find(e.v)) continue;
        sum += e.c;
        unionn(e.u, e.v);
    }
    printf("%lld\n", sum);
    
    return 0;
}