1 #include <map>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <iostream>
 5 using namespace std;
 6 map<string, int> mmap; 
 7 int pic[1550][1550], dis[1550], vis[1550];
 8 const int INF = 0x3f3f3f3f;
 9 int Dijkstra(int src, int end, int k)
10 {
11     memset(vis, 0, sizeof(vis));
12     for(int i = 1; i < k; i++)
13         dis[i] = pic[src][i];
14     vis[src] = 1;
15     for(int i = 1; i < k - 1; i++)
16     {
17         int temp, min = INF;
18         for(int j = 1; j < k; j++)
19         {
20             if(!vis[j]&&dis[j]<min)
21             {
22                 min = dis[j];
23                 temp = j;
24             //    printf("%d\n", temp);
25             }
26         }
27         vis[temp] = 1;
28         for(int j = 1; j < k; j++)
29             if(!vis[j] && dis[j] > dis[temp] + pic[temp][j])
30                 dis[j] = dis[temp] + pic[temp][j];
31         
32     }
33     return dis[end]==INF?-1:dis[end];
34 }
35 int main()
36 {
37     int t, k, sta, end;;
38     while(~scanf("%d", &t), t != -1)
39     {
40         for(int i = 1; i < 155; i++)
41             for(int j = 1; j < 155; j++)
42                 pic[i][j]=(i==j?0:INF);
43         k = 1; mmap.clear();
44            char a[110], b[110]; int c;  // map存东西时要从1开始， important; 
45         cin >> a >> b; 
46         if(!mmap[a]) mmap[a] = k++;
47         sta = k-1;
48         if(!mmap[b]) mmap[b] = k++;
49         end = k-1;
50         // printf("%d %d", mmap[a], mmap[b]);    
51          for(int i = 0; i < t; i++)
52         {
53             cin >> a >> b >> c;
54             if(!mmap[a]) mmap[a] = k++;
55             if(!mmap[b]) mmap[b] = k++;
56             if(pic[mmap[a]][mmap[b]] > c)
57                 pic[mmap[a]][mmap[b]] = pic[mmap[b]][mmap[a]] = c;
58         }  
59         printf("%d\n", Dijkstra(sta, end, k)); 
60     }
61     return 0;
62 }