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#include<cstdio>
#include<algorithm>
#include<iostream>
#include<fstream>
#include<iomanip>
#include<vector>
#include<map>
#include<set>
#include<stack>

#define SC(n) scanf("%d", &n)
#define SC2(n, m) scanf("%d %d", &n, &m)
#define SCC(c) scanf(" %c", &c)
#define SCS(b) scanf("%s", b)
#define REP(i, n) for(int i = 0; i < (n); ++i)
#define FORE(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define FORIT(i, c, typ) for(typ::iterator i = c.begin(); i != c.end(); ++i)
#define PR(n) printf("%d ", (int) (n)) 
#define PRN(n) printf("%d\n", (int) (n)) 
#define elif else if
#define pb push_back
#define mp make_pair
#define xx first
#define yy second
#define all(v) v.begin(), v.end()
#define itr iterator
#define DBG if(0) printf

using namespace std;

typedef unsigned int uint;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> pi;
typedef vector<pi> vpi;
typedef pair<int, pi> pii;
typedef vector<pii> vpii;
typedef vector<vpi> vvpi;
typedef map<int, vpi> mvpi;

const int MMAX = 4000*1000 + 7, NMAX = 2007;

int n, k, x, y, w;
pii e[MMAX];
int par[NMAX], size[NMAX]; 
ll ans;

inline int getPar(int x) {
	int y = x;
	while(x != par[x])
		x = par[x];
	while(y != x) {
		int z = par[y];
		par[y] = x;
		y = z;
	}
	return x;
}

inline void connect(int x, int y) {
	x = getPar(x);
	y = getPar(y);
	if(size[x] > size[y]) {
		par[y] = x;
		size[x] += size[y];
	}
	else {
		par[x] = y;
		size[y] += size[x];
	}
}

int main() {
	SC(n);
	k = 0;
	
	REP(i, n)
		FORE(j, i+1, n) {
			SC(w);
			e[k++] = mp(w, mp(i,j));
		}
	sort(e, e+k);
	
	REP(i, n+1) {
		par[i] = i;
		size[i] = 1;
	}
	
	REP(i, k) {
		x = e[i].yy.xx;
		y = e[i].yy.yy;
		if(getPar(x) != getPar(y)) {
			ans += e[i].xx;
			connect(x,y);
		}
	}
	printf("%lld", ans);
	//cout << ans;
	return 0;
}