1 #include<iostream>
 2 #include<cstdio>
 3 #include<map>
 4 #include<string>
 5 #include<cstring>
 6 #define N 155
 7 #define INF 0x1fffffff
 8 using namespace std;
 9 int mp[N][N];
10 bool p[N];
11 int dist[N];
12 void dijk(int s , int n)
13 {
14     int i , j , k ;
15     for( i = 1 ; i <= n ;i++)
16     {
17         p[i] = false;
18         dist[i] = mp[s][i];
19     }
20     p[s] = true;
21     dist[s] = 0;
22     for(i = 1 ; i < n ; i++)
23     {
24         int Min = INF;
25         int k = 0 ;
26         for( j = 1 ; j <= n ;j++)
27         {
28             if(!p[j]&&dist[j]<Min)
29             {
30                 Min = dist[j];
31                 k = j;
32             }
33         }
34         if(Min==INF) return ;
35         p[k] = true;
36         for(j = 1 ; j <= n ;j++)
37         {
38             if(!p[j]&&mp[k][j]!=INF&&dist[j]>dist[k]+mp[k][j])
39                 dist[j] = dist[k]+mp[k][j];
40         }
41     }
42 }
43 map < string ,int > city;
44 int main()
45 {
46     int n ;
47     while(~scanf("%d",&n)&&n!=-1)
48     {
49         int cnt = 1 ;
50         city.clear();
51         string ss, tt;
52         cin>>ss>>tt;
53         if(city.find(ss)==city.end())
54             city[ss] = cnt++;
55         if(city.find(tt)==city.end())
56             city[tt] = cnt++;
57         int l ;
58         string s , t ;
59         for(int i = 0; i < N; i++) for(int j = 0; j < N; j++) mp[i][j] = ((i==j) ? 0 : INF);
60         for(int i = 0 ;i < n ;i++)
61         {
62             cin>>s>>t>>l;
63             if(city.find(s)==city.end())
64                 city[s] = cnt++;
65             if(city.find(t)==city.end())
66                 city[t] = cnt++;
67             int sid = city[s], tid = city[t];//这样会减少复杂度
68             //printf("%d %d\n",sid, tid);
69             if(mp[sid][tid] > l) mp[sid][tid] = mp[tid][sid] = l;
70         }
71 
72         dijk(city[ss], city.size());
73         if(dist[city[tt]]!=INF)
74             printf("%d\n",dist[city[tt]]);
75         else printf("-1\n");
76     }
77     return 0 ;
78 }