# include <cstdio>

 # include <cmath>

 # include <iostream>

 # include <cstring>

 # include <algorithm>

 using namespace std ;

 int l = ,flag = ;

 struct Node

 {

     char head,end;

 } c[];

 int vis[];

 void dfs(char ch)

 {

     int i;

     if(ch == 'm')

         flag = ;

     if(flag)

         return;

     for(i = ; i<l; i++)

     {

         if(vis[i])

             continue;

         if(c[i].head == ch)

         {

             vis[i] = ;

             dfs(c[i].end);

             vis[i] = ;

         }

     }

 }

 int main()

 {

     //freopen("in.txt","r",stdin) ;

     char s[];

     int i;

     while(~scanf("%s",s))

     {

         if(!strcmp(s,""))

             continue;

         l = ;

         c[l].head = s[];

         c[l].end = s[strlen(s)-];

         l++;

         while(scanf("%s",s))

         {

             if (strcmp(s,"") == )

                 break ;

             c[l].head = s[];

             c[l].end = s[strlen(s)-];

             l++;

         }

         flag = ;

         for(i = ; i<l; i++)

         {

             if(c[i].head == 'b')

             {

                 memset(vis,,sizeof(vis));

                 vis[i] = ;

                 dfs(c[i].end);

             }

             if(flag)

                 break;

         }

         if(flag)

             printf("Yes.\n");

         else

             printf("No.\n");

     }

     return ;

 }