#include<iostream>
#include<cstdio>
#include<cmath>
#include<map>
#include<cstdlib>
#include<vector>
#include<set>
#include<queue>
#include<cstring>
#include<string.h>
#include<algorithm>
#define INF 0x3f3f3f3f
typedef long long ll;
typedef unsigned long long LL;
using namespace std;
const int N = 1e6+10;
const ll mod = 1e9+7;
int t=0,flag=0;
struct Node
{
    char head,next;
}c[10000];
int vis[10000];
void DFS(char ch)
{
    if(ch==‘m‘){
        flag=1;
        return;
    }
    for(int i=0;i<t;i++)
    {
        if(vis[i])
            continue;
        if(c[i].head==ch){
            vis[i] = 1;
            DFS(c[i].next);
            vis[i]=0;
        }
    }
}
int main()
{
    char s[100];
    int i;
    while(~scanf("%s",s))
    {
        if(s[0]==‘0‘)continue;
        t=0;
        int len=strlen(s);
        c[t].head=s[0];
        c[t].next=s[len-1];
        t++;
        while(scanf("%s",s),strcmp(s,"0"))
        {
            len=strlen(s);
            c[t].head=s[0];
            c[t].next=s[len-1];
            t++;
        }
        flag=0;
        for(int i=0;i<t;i++)
        {
            if(c[i].head == ‘b‘)
            {
                memset(vis,0,sizeof(vis));
                vis[i] = 1;
                DFS(c[i].next);
            }
            if(flag)
                break;
        }
        if(flag)
            printf("Yes.\n");
        else
            printf("No.\n");
    }

    return 0;
}