1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #define M 160
 5 #define MAX 0x3f3f3f3f
 6 using namespace std;
 7 int m;
 8 int map[M][M],vis[M],dis[M];
 9 char place[M][35];
10 
11 int find(char s[])  //关键处理，将字符串数组转换为整数数组存储
12 {
13     int i;
14     for(i=1; i<=m; i++)
15     {
16         if(strcmp(s,place[i])==0)
17             return i;
18     }
19     strcpy(place[++m],s);
20     return m;
21 }
22 
23 int main()
24 {
25     int n,i,j,f,e;
26     char s[35];
27     while(~scanf("%d",&n))
28     {
29         if(n==-1) break;
30         m=0;
31         scanf("%s",s),f=find(s);
32         scanf("%s",s),e=find(s);
33         memset(vis,0,sizeof(vis));
34         memset(dis,0,sizeof(dis));
35         for(i=1; i<=150; i++)
36             for(j=1; j<=150; j++)
37             {
38                 if(i==j) map[i][j]=0;
39                 else     map[i][j]=MAX;
40             }
41         int a,b,c;
42         while(n--)
43         {
44             scanf("%s",s),a=find(s);
45             scanf("%s",s),b=find(s);
46             scanf("%d",&c);
47             if(map[a][b]>c)
48                 map[a][b]=c,map[b][a]=c;
49         }
50         vis[f]=1;
51         for(i=1; i<=m; i++)
52             dis[i]=map[f][i];
53         int min,t;
54         for(i=1; i<=m; i++)
55         {
56             min=MAX;
57             for(j=1; j<=m; j++)
58                 if(!vis[j]&&dis[j]<min)
59                 {
60                     min=dis[j];
61                     t=j;
62                 }
63             vis[t]=1;
64             for(j=1; j<=m; j++)
65                 if(!vis[j]&&map[t][j]<MAX)
66                     if(dis[j]>dis[t]+map[t][j])
67                         dis[j]=dis[t]+map[t][j];
68         }
69         if(dis[e]<MAX)
70             printf("%d\n",dis[e]);
71         else
72             printf("-1\n");
73     }
74     return 0;
75 }