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杭电2112
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 1 //杭电2112
 2 #include<stdio.h>
 3 #include<string.h>
 4 #include<stdlib.h>
 5 #define M 99999999
 6 #define N 160
 7 char s[N][50];
 8 int a[N],b[N],map[N][N];
 9 int n,t,num,k,p,d;
10 int MIN(int a,int b)
11 {
12     return a<b?a:b;
13 }
14 int look(char a[])
15 {
16     int i;
17     for(i=1;i<k;i++)
18         if(strcmp(a,s[i])==0)
19             break;
20         if(i==k)
21         {
22             strcpy(s[k],a);
23         k++;
24         }
25         return i;
26 }
27 void power()
28 {
29     char s1[50],s2[50];
30     int i,j,x,y;
31     scanf("%s%s",s1,s2);
32     if(strcmp(s1,s2)==0)
33         p=1;
34     strcpy(s[1],s1);
35     strcpy(s[2],s2);
36     k=3;
37     for(i=0;i<n;i++)
38     {
39         scanf("%s%s%d",s1,s2,&d);
40         x=look(s1);
41         y=look(s2);
42         map[x][y]=map[y][x]=d;
43     }
44 }
45 int main()
46 {
47     int i,j,t,min,num;
48     while(scanf("%d",&n),n!=-1)
49     {
50         for(i=1;i<151;i++)
51             for(j=1;j<151;j++)
52             {
53                 if(i==j)
54                     map[i][j]=0;
55                 else
56                     map[i][j]=M;
57             }
58             p=0;
59             power();
60             if(p==1)
61                 printf("0\n");
62             else
63             {
64                 memset(b,0,sizeof(b));
65                 for(i=1;i<k;i++)
66                     a[i]=M;
67                 t=j=1;
68                 num=1;
69                 b[1]=1;
70                 a[1]=0;
71                 while(num<k-1)
72                 {
73                     min=M;
74                     for(i=2;i<k;i++)
75                     {
76                         if(b[i]==0&&map[t][i])
77                         {
78                             a[i]=MIN(a[i],a[t]+map[t][i]);//找出最短路径
79                             if(min>a[i])
80                             {
81                                 min=a[i];
82                                 j=i;
83                             }
84                         }
85                     }
86                     b[j]=1;

87                     if(t==j||j==2)
88                         break;
89                     t=j;
90                     num++;
91                 }
92                 if(a[2]!=M)
93                     printf("%d\n",a[2]);
94                 else
95                     printf("-1\n");
96             }
97     }
98     return 0;
99 }