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//Krzysztof Pieprzak
#include <iostream>
#include <fstream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <string>
#include <cstring>
#include <vector>
#include <queue>
#include <set>
#include <list>
#include <deque>
#include <stack>
#include <map>
#include <ctime>
#include <cassert>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
typedef unsigned int uint;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int,int> pii;
typedef pair<long long, long long> pll;
typedef vector<pii> vpii;
typedef vector<pll> vpll;

#define Size(x) (int)x.size()
#define VAR(v,n) typeof(n)v = (n)
#define FOR(i,a,b) for(VAR(i,a); i < (b); ++i)
#define FORE(i,a,b) for(VAR(i,a); i <= (b); ++i)
#define FORREV(i,a,b) for(VAR(i,b); i >= (a); --i)
#define FORSTEP(i,a,b,step) for(VAR(i,a); i < (b); i += (step))
#define FOREACH(i,c) for(VAR(i,(c).begin()); i != (c).end(); ++i)
#define ALL(x) x.begin(),x.end()
#define CLEAR(t) memset(t, 0, sizeof(t))
#define F first
#define S second
#define MP make_pair
#define PUB push_back
#define POB pop_back
#define pieprzu ios_base::sync_with_stdio(0);

const int    INF = 1000000001;
const double EPS = 10e-9;

const int MAXN = 2005;

int t[MAXN][MAXN];
pair<int,pii> s[MAXN*MAXN];

pii eq[MAXN];
pii res[MAXN];
bool vis[MAXN];
int LAST;

inline bool check(pii p, int n)
{
    for (int i = p.F; i < n; i = p.F)
    {
        if (LAST < p.F)
        {
            return false;
        }
        if (eq[i].F == -1)
        {
            eq[i] = p;
            if (i == LAST) for (; LAST >= 0 && eq[LAST].F != -1; --LAST);
            return true;
        }
        else if (eq[i] == p)
        {
            return false;
        }
        else
        {
            p.F = min(p.S,eq[i].S)+1;
            p.S = max(p.S,eq[i].S);
        }
    }
    return false;
}

void rob()
{
    int n;
    scanf("%d", &n);

    int cnt = 0;
    FOR (i, 0, n)
        FOR (j, i, n)
        {
            scanf("%d", &t[i][j]);
            s[cnt++] = MP(t[i][j],MP(i,j));
        }
    sort(s,s+cnt);

    FOR (i, 0, n) eq[i] = MP(-1,-1);
    LAST = n-1;

    ll res = s[0].F;
    check(s[0].S,n);
    int cnt2 = 1;
    FOR (i, 1, cnt)
    {
        if (check(s[i].S,n))
        {
            res += s[i].F;
            ++cnt2;
            if (cnt2 == n) break;
        }
    }

    //printf("%d\n", cnt2);
    //FOR (i, 0, cnt2) printf("(%d,%d) ", sol[i].F, sol[i].S);printf("\n");
    printf("%lld\n", res);
}

int main()
{
    int test = 1;
    //scanf("%d", &test);

    while (test--) rob();

    return 0;
}