1 #include<map>
 2 #include<iostream>
 3 #include<string>
 4 #include<cstdio>
 5 #include<cstring>
 6 #include<algorithm>
 7 using namespace std;
 8 
 9 const int inf=0x3f3f3f3f;
10 int G[155][155],vis[155],d[155];
11 map<string,int>edges;
12 int t,n;
13 
14 int dijkstra(int S,int T)
15 {
16     int u,i,j;
17     memset(vis,0,sizeof(vis));
18     //memset(d,0,sizeof(d));
19     for(i=0;i<=t;i++)
20     d[i]=G[S][i];
21     d[S]=0;
22     vis[S]=1;
23     for(i=1;i<n;i++)
24     {
25         int temp=inf;
26         for(j=0;j<=t;j++)
27         {
28             if(!vis[j]&&d[j]<temp)
29             {
30                 temp=d[j];
31                 u=j;
32             }
33         }
34         if(temp==inf)
35         continue;
36         vis[u]=true;
37         for(j=0;j<=t;j++)
38         {
39             if(!vis[j]&&d[u]+G[u][j]<d[j])
40             d[j]=d[u]+G[u][j];
41         }
42     }
43     return d[T];
44 }
45 
46 int main()
47 {
48     int i,S,T,num;
49     string s1,s2;
50 //    freopen("in.txt","r",stdin);
51     while(scanf("%d",&n)&&n!=-1)
52     {
53         t=-1;
54         edges.clear();
55         memset(G,inf,sizeof(G));
56         cin>>s1>>s2;
57         edges[s1]=++t;
58         S=t;
59         if(!edges.count(s2))
60         edges[s2]=++t;
61         T=t;
62         for(i=0;i<n;i++)
63         {
64             cin>>s1>>s2>>num;
65             if(!edges.count(s1))
66             edges[s1]=++t;
67             if(!edges.count(s2))
68             edges[s2]=++t;
69             G[edges[s2]][edges[s1]]=G[edges[s1]][edges[s2]]=min(num,G[edges[s1]][edges[s2]]);
70         }
71         int ans=dijkstra(S,T);
72         if(ans==inf)
73         printf("-1\n");
74         else
75         printf("%d\n",ans);
76     }
77     return 0;
78 }