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#include <cstdio>
#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <set>
#include <bitset>
#include <map>
#include <list>
#include <stack>
#include <queue>
#include <deque>
#include <complex>
#include <iterator>
#include <tr1/unordered_map>


using namespace std;

typedef vector<int> VI;
typedef long long LL;

#define FOR(x,b,e) for(int x=b; x<=(e); ++x)
#define FORD(x,b,e) for(int x=b; x>=(e); --x)
#define REP(x,n) for(int x=0; x<(n); ++x)
#define VAR(x,n) __typeof(n) x = (n)
#define ALL(c) (c).begin(), (c).end()
#define SIZE(c) ((int)(c).size())
#define FOREACH(i,c) for(VAR(i, (c).begin()); i!=(c).end(); ++i)
#define PB push_back
#define PF push_front
#define ST first
#define ND second
#define MP make_pair
#define MIN(a,b) ((a) < (b) ? (a) : (b))
#define MAX(a,b) ((a) > (b) ? (a) : (b))

#define N 2002

struct interval {
    int val;
    int beg;
    int end;
};

struct comp {
    bool operator() (const interval& i1, const interval& i2){
        if(i1.val != i2.val)
            return i1.val < i2.val;
        else if(i1.end != i2.end)
            return i1.end > i2.end;
        else
            return i1.beg < i1.beg;
    }
} comp;

interval priority[N*N];
map<int, int> space;

int check(int a, int b){
    map<int, int>::iterator it;
    while(1){
        it = space.find(a);
        if(it==space.end()){
            space.insert(it, MP(a,b));
            return 1;
        }
        else {
            a = MIN(b, it->second);
            b = MAX(b, it->second);
            if(a==b)
                return 0;
        }
    }
    return 0;
}

int main(){
    int n, rescount, k, act;
    LL res = 0;
    scanf("%d ", &n);
    k = 0;
    REP(i,n)
        FOR(j,i,n-1){
            scanf("%d ", &priority[k].val);
            priority[k].beg = i;
            priority[k++].end = j;
        }

    sort(priority, priority+k, comp);

    rescount = act = 0;
    space.insert(MP(n,n));
    while(rescount < n){
        interval inter = priority[act++];
        if(check(inter.beg,inter.end+1)){
            res += inter.val;
            rescount++;
        }
    }
    printf("%lld\n", res);
    return 0;
}