//#include <bits/stdc++.h>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <string>
#include <stdio.h>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <string.h>
#include <vector>
#define ME(x , y) memset(x , y , sizeof(x))
#define SF(n) scanf("%d" , &n)
#define rep(i , n) for(int i = 0 ; i < n ; i ++)
#define INF  0x3f3f3f3f
#define mod 1000000007
#define PI acos(-1)
using namespace std;
typedef long long ll ;
char s[1009] ;
int vis[1009];
int flag ;
int l ;

struct node
{
    char he , ba ;
}a[1009];

void dfs(int d , int ans)
{
    if(a[d].ba == ‘m‘ && ans != 0)
    {
        flag = 1 ;
        return ;
    }
    if(flag)
        return ;
    for(int i = 0 ; i < l ; i++)
    {
        if(a[d].ba == a[i].he && !vis[i])
        {
            vis[i] = 1 ;
            dfs(i , ans+1);
        }
    }
    vis[d] = 0 ;
}

int main()
{
    while(~scanf("%s" , s))
    {
        if(strcmp(s , "0") == 0)
            continue ;
        memset(a , ‘\0‘ , sizeof(a));
        memset(vis , 0 , sizeof(vis));
        flag = 0;
        l = 0 ;
        int len = strlen(s);
        a[l].he = s[0];
        a[l].ba = s[len-1];
        l++ ;
        while(~scanf("%s" , s) && strcmp(s , "0"))
        {
            len = strlen(s);
            a[l].he = s[0];
            a[l].ba = s[len-1];
            l++;
        }

        for(int i = 0 ; i < l ; i++)
        {
            if(a[i].he == ‘b‘)
            {
                vis[i] = 1 ;
                dfs(i , 0);
            }
        }
        if(flag)
            cout << "Yes." << endl ;
        else
            cout << "No." << endl ;
    }

    return 0;
}