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#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <set>
#include <queue>
#include <map>
#include <cstdio>
#include <iomanip>
#include <sstream>
#include <iostream>
#include <cstring>
#define REP(i,x,v)for(int i=x;i<=v;i++)
#define REPD(i,x,v)for(int i=x;i>=v;i--)
#define FOR(i,v)for(int i=0;i<v;i++)
#define FORE(i,t) for (typeof(t.begin()) i=t.begin(); i!=t.end(); i++)
#define FOREACH(i,t) FORE(i,t)
#define REMIN(x,y) (x)=min((x),(y))
#define REMAX(x,y) (x)=max((x),(y))
#define pb push_back
#define sz size()
#define mp make_pair
#define fi first
#define se second
#define ll long long
#define IN(x,y) ((y).find((x))!=(y).end())
#define un(v) v.erase(unique(ALL(v)),v.end())
#define LOLDBG
#ifdef LOLDBG
#define DBG(vari) cerr<<#vari<<" = "<<vari<<endl;
#define DBG2(v1,v2) cerr<<(v1)<<" - "<<(v2)<<endl;
#else
#define DBG(vari)
#define DBG2(v1,v2)
#endif
#define CZ(x) scanf("%d",&(x));
#define CZ2(x,y) scanf("%d%d",&(x),&(y));
#define CZ3(x,y,z) scanf("%d%d%d",&(x),&(y),&(z));
#define ALL(x) (x).begin(),(x).end()
#define tests int dsdsf;cin>>dsdsf;while(dsdsf--)
#define testss int dsdsf;CZ(dsdsf);while(dsdsf--)
using namespace std;
typedef pair<int,int> pii;
typedef vector<int> vi;
template<typename T,typename TT> ostream &operator<<(ostream &s,pair<T,TT> t) {return s<<"("<<t.first<<","<<t.second<<")";}
template<typename T> ostream &operator<<(ostream &s,vector<T> t){s<<"{";FOR(i,t.size())s<<t[i]<<(i==t.size()-1?"":",");return s<<"}"<<endl; }

/////////////////////
////// INPUT ////////
////////////////////
typedef unsigned long long ull;
class INPUT {
static const int BUFSIZE = 1<<16;
static char buffer[];
char *bufpos;
char *bufend;
void grabBuffer();
public:
INPUT() { grabBuffer(); }
bool eof() { return bufend==buffer; }
char nextChar() { return *bufpos; }
inline char readChar();
inline void skipWS();
unsigned readUnsigned();
int readInt();
ull readULL();
};

char INPUT::buffer[INPUT::BUFSIZE];

void INPUT::grabBuffer() {
bufpos = buffer;
bufend = buffer + fread( buffer, 1,BUFSIZE,stdin);
}

char INPUT::readChar() {
char res = *bufpos++;
if(bufpos==bufend) grabBuffer();
return res;
}

inline bool myisspace(char c) { return c<=' '; }

void INPUT::skipWS() {
while(!eof() && myisspace(nextChar())) readChar();
}

unsigned INPUT::readUnsigned() {
skipWS();
unsigned res = 0;
while(!eof() && isdigit(nextChar())) {
res = 10u * res + (readChar()-'0');
}
return res;
}

ull INPUT::readULL() {
skipWS();
ull res = 0;
while(!eof() && isdigit(nextChar())) {
res = 10ULL * res + (readChar()-'0');
}
return res;
}

int INPUT::readInt() {
	skipWS();
	bool neg = false;
	if(!eof() && nextChar()=='-') { neg=true; readChar(); }
	int res = static_cast<int>(readUnsigned());
	if(neg) res = -res;
	return res;
}

/////////////////////
////// OUTPUT //////
////////////////////

class OUTPUT {
static const int BUFSIZE = 1<<16;
static char buffer[];
char *bufpos;
char *BUFLIMIT;
void flushBuffer();
public:
	OUTPUT():bufpos(buffer),BUFLIMIT(buffer+BUFSIZE-100) {}
	~OUTPUT() { flushBuffer(); }
	inline void operator()(char c);
	inline void operator()(unsigned x);
	inline void operator()(int x);
	inline void operator()(unsigned long long int x);
	inline void operator()(long long int x);
	inline void operator()(const char*s);
	void operator()(const string&s) { operator()(s.c_str()); }
	template<class A,class B>
	void operator()(const A& a,const B& b) {
		operator()(a); operator()(b);
	}
	template<class A,class B,class C>
	void operator()(const A& a,const B& b,const C&c) {
		operator()(a); operator()(b); operator()(c);
	}
	template<class A,class B,class C,class D>
	void operator()(const A& a,const B& b,const C&c,const D&d) {
		operator()(a); operator()(b); operator()(c); operator()(d);
	}
	template<class A,class B,class C,class D,class E>
	void operator()(const A& a,const B& b,const C&c,const D&d,const E&e) {
		operator()(a); operator()(b); operator()(c); operator()(d); operator()(e);
	}
	template<class A,class B,class C,class D,class E,class F>
	void operator()(const A& a,const B& b,const C&c,const D&d,const E&e,const F&f) {
		operator()(a); operator()(b); operator()(c); operator()(d); operator()(e); operator()(f);
	}
};

char OUTPUT::buffer[OUTPUT::BUFSIZE];

void OUTPUT::flushBuffer() {
	char *p = buffer;
	while(p < bufpos) {
		p += fwrite( p,1, bufpos-p,stdout);
	}
	bufpos = buffer;
}

void OUTPUT::operator()(char c) {
	*bufpos = c;
	++bufpos;
	if(bufpos >= BUFLIMIT) flushBuffer();
}

void OUTPUT::operator()(unsigned x) {
	char *old = bufpos;
	do {
		*bufpos = char('0' + x % 10u);
		x /= 10u;
		++bufpos;
	} while(x);
	reverse(old, bufpos);
	if(bufpos >= BUFLIMIT) flushBuffer();
}

void OUTPUT::operator()(int x) {
	if(x<0) { operator()('-'); x = -x; }
	operator()(static_cast<unsigned>(x));
}

void OUTPUT::operator()(unsigned long long int x) {
	char *old = bufpos;
	do {
		*bufpos = char('0' + x % 10u);
		x /= 10u;
		++bufpos;
	} while(x);
	reverse(old, bufpos);
	if(bufpos >= BUFLIMIT) flushBuffer();
}

void OUTPUT::operator()(long long int x) {
	if(x<0) { operator()('-'); x = -x; }
	operator()(static_cast<unsigned long long int>(x));
}

void OUTPUT::operator()(const char*s) {
	while(*s) operator()(*s++);
}

INPUT input;
OUTPUT output;

int d[2222][2222];
int opt[2222];
#define INF 1000000002

int main()
{

    int n=input.readInt();
    //int n=2000;
    FOR(i,n)
    {
        REP(j,i+1,n)
        {
            int x=input.readInt();
            //int x=rand()+30000*rand()+(1<<25);
            d[i][j]=d[j][i]=x;
        }
    }
    ll w=0;
    opt[0]=INF;
    REP(i,1,n)opt[i]=d[0][i];
    REP(f,1,n)
    {
        int best=0;
        FOR(i,n+1) if (opt[i]<opt[best]) best=i;
        w+=opt[best];
        opt[best]=INF;
        FOR(i,n+1) if (opt[i]!=INF) REMIN(opt[i],d[best][i]);
    }
    output(w);

    return 0;
}