# include <iostream>

 # include <cstdio>

 # include <cstring>

 # include <string>

 # include <algorithm>

 # include <cmath>

 # include <queue>

 # include <map>

 # define LL long long

 using namespace std ;

 const int INF=0x3f3f3f3f;

 const int MAXN=;

 int n ;

 map<string,int> mp ;

 bool vis[MAXN];

 int cost[MAXN][MAXN] ;

 int lowcost[MAXN] ;

 void Dijkstra(int beg)

 {

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

     {

         lowcost[i]=INF;vis[i]=false;

     }

     lowcost[beg]=;

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

     {

         int k=-;

         int Min=INF;

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

             if(!vis[i]&&lowcost[i]<Min)

             {

                 Min=lowcost[i];

                 k=i;

             }

             if(k==-)

                 break ;

             vis[k]=true;

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

                 if(!vis[i]&&lowcost[k]+cost[k][i]<lowcost[i])

                 {

                     lowcost[i]=lowcost[k]+cost[k][i];

                 }

     }

 }

 int main ()

 {

    // freopen("in.txt","r",stdin) ;

    int m ;

    while(cin>>m)

    {

        if (m == -)

         break ;

        mp.clear() ;

        string s1 ,s2 ;

        int i , j , w ;

        for (i =  ; i < MAXN ; i++)

         for (j =  ; j < MAXN ; j++)

        {

            if (i == j)

               cost[i][j] =  ;

            else

               cost[i][j] = INF ;

        }

        cin>>s1>>s2 ;

        mp[s1] =  ;

        mp[s2] =  ;

        n =  ;

        bool flag =  ;

        if (s1 == s2)

           flag =  ;

        while(m--)

        {

            cin>>s1>>s2>>w ;

            if (!mp[s1])

                mp[s1] = n++ ;

            if (!mp[s2])

                mp[s2] = n++ ;

            if (w < cost[mp[s1]-][mp[s2]-])

            {

                cost[mp[s1]-][mp[s2]-] = w ;

                cost[mp[s2]-][mp[s1]-] = w ;

            }

        }

        n-- ;

        if (flag)

        {

            cout<<<<endl ;

            continue ;

        }

        Dijkstra() ;

        if (lowcost[] != INF)

           cout<<lowcost[]<<endl ;

        else

           cout<<-<<endl ;

    }

     return  ;

 }