1 #include<stdio.h>
 2 #include<string.h>
 3 int map[30][30];
 4 int visit[30],flot;
 5 char s[100010];
 6 void dfs(int x){
 7     if(x==‘m‘-‘a‘){
 8         flot=1;
 9         return;
10     }
11     for(int i=0;i<26;i++){
12         if(map[x][i]&&!visit[i]){
13             visit[i]=1;
14             dfs(i);
15             visit[i]=0;
16         }
17     }
18     return;
19 }
20 int main(){flot=0;int x,y,t;
21     while(~scanf("%s",s)){
22         if(!strcmp(s,"0")){
23             dfs(‘b‘-‘a‘);
24             if(flot)puts("Yes.");
25             else puts("No.");
26             flot=0;
27             memset(map,0,sizeof(map));
28             memset(visit,0,sizeof(visit));
29         }t=strlen(s);
30         x=s[0]-‘a‘;y=s[t-1]-‘a‘;
31         map[x][y]=1;
32     }
33     return 0;
34 }