#include <queue>

#include <cstdio>

#include <cstring>

#include <iostream>

#include <algorithm>

using namespace std;

struct EdgeType {

    int to,dis,next;

};

struct EdgeType edge[**];

int if_z,n,head[],cnt=;

char Cget;

inline void in(int &now)

{

    now=,if_z=,Cget=getchar();

    while(Cget>''||Cget<'')

    {

        if(Cget=='-') if_z=-;

        Cget=getchar();

    }

    while(Cget>=''&&Cget<='')

    {

        now=now*+Cget-'';

        Cget=getchar();

    }

    now*=if_z;

}

inline void edge_add(int u,int v,int w)

{

    cnt++;

    edge[cnt].to=v;

    edge[cnt].dis=w;

    edge[cnt].next=head[u];

    head[u]=cnt;

}

int spfa()

{

    queue<int>que;

    bool if_[];

    int cost[];

    memset(cost,0x7f,sizeof(cost));

    que.push();if_[]=true,cost[]=;

    while(!que.empty())

    {

        int pos=que.front();que.pop();

        for(int i=head[pos];i;i=edge[i].next)

        {

            if(edge[i].dis+cost[pos]<cost[edge[i].to])

            {

                cost[edge[i].to]=edge[i].dis+cost[pos];

                if(!if_[edge[i].to])

                {

                    que.push(edge[i].to);

                    if_[edge[i].to]=true;

                }

            }

        }

        if_[pos]=false;

    }

    return cost[n];

}

int main()

{

    in(n);int pos;

    for(int i=;i<n;i++)

    {

        for(int j=i+;j<=n;j++)

        {

            in(pos);

            edge_add(i,j,pos);

        }

    }

    cout<<spfa();

    return ;

}