1 #pragma warning (disable :4786)
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<iostream>
 5 #include<map>
 6 #include<string>
 7 using namespace std;
 8
 9 const int inf=0x3f3f3f3f;
10 const int tol=152;
11 int path[tol],lowc[tol];
12 int sta[tol][tol];
13 map<string,int>sav;
14 void Dijkstra( int n,int beg )
15 {
16     int i,j,minc;
17     int vis[tol]={0};
18     vis[beg]=1;
19     for(i=0;i<n;i++)
20     {
21         lowc[i]=sta[beg][i];
22         path[i]=beg;
23     }
24     lowc[beg]=0;
25     path[beg]=-1;
26     int pre=beg;
27     for(i=1 ; i<n ;i++)
28     {
29         minc=inf;
30         for(j=0;j<n;j++)
31         {
32             if(vis[j]==0&&lowc[pre]+sta[pre][j]<lowc[j])
33             {
34                 lowc[j]=lowc[pre]+sta[pre][j];
35                 path[j]=pre;
36             }
37         }
38         for(j=0;j<n;j++)
39         {
40             if(vis[j]==0&&lowc[j]<minc)
41             {
42                 minc=lowc[j];
43                 pre=j;
44             }
45         }
46         vis[pre]=1;
47     }
48 }
49
50 int main( void )
51 {
52     int t,e,cc,i,j;
53     string str,en;
54     string aa,bb;
55     while(cin>>t,t!=-1)
56     {
57         cin>>str>>en;
58          e=2;
59          for(i=0;i<tol;i++)
60          {
61              for(j=0;j<tol;j++)
62                  sta[i][j]=inf;
63          }
64         while(t--)
65         {
66             cin>>aa>>bb>>cc;
67             if(sav[aa]==0) sav[aa]=e++;
68             if(sav[bb]==0) sav[bb]=e++;
69              if(sta[sav[aa]-1][sav[bb]-1]>cc)
70          sta[sav[aa]-1][sav[bb]-1]=sta[sav[bb]-1][sav[aa]-1]=cc;
71         }
72     /*    map<string,int>::iterator it;
73         for(it=sav.begin();it!=sav.end();it++)
74         {
75             cout<<it->first<<endl;
76         }*/
77         sta[sav[str]-1][0]=sta[0][sav[str]-1]=0; //扩充图
78         sta[sav[en]-1][e-1]=sta[e-1][sav[en]-1]=0;
79         sav.clear();
80         Dijkstra(e,0);
81         if(lowc[e-1]==inf) cout<<-1<<endl;
82         else
83         cout<<lowc[e-1]<<endl;
84     }
85     return 0;}