/* 
 * File:   main.cpp
 * Author: cteam027
 *
 * Created on October 22, 2016, 9:21 AM
 */

#include <cstdlib>
#include <iostream>
using namespace std;

/*
 * 
 */
struct Card{
    Card( char r, char s ) : rank( r ), suit( s ), next( NULL ) {}
    char rank;
    char suit;
    Card * next;
    bool match(Card * card){
        return card->rank == rank || card->suit == suit;
    }
    
};

void Join( Card * tmp, Card * tmpNext, Card * c )
{
    c -> next = tmpNext;
    tmp -> next = c;
}

bool Sort( Card *& head, Card *& c )
{
    if( !head ) 
    {
        head = c;
        return true;
    }
    Card * tmp = head;
    while( tmp )
    {
        if( tmp == head )
        {
            if( tmp -> match(c) )
            {
                c -> next = tmp;
                head = c;
                return true;
            }
        }
        if( !(tmp -> next)  )
        {
            if( tmp -> match( c ) )
            {
              tmp -> next = c;  
              return true;
            }
        }
        if( tmp -> match( c ) && tmp -> next -> match( c )) 
        {
            Join( tmp, tmp -> next, c );
            return true;
        }
        tmp = tmp -> next;
    }
    return false;
}

int main(int argc, char** argv) {
    int n;
    Card * head = NULL, * tmp = NULL;
    while( (cin . good()) )
    {
      cin >> n;
      if( !cin . good() ) break;
      char rank, suit;
      bool check = true;
      for( int i = 0; i < n; i++ )
      {
          cin >> rank >> suit ;
          //cout << rank << " " << suit << endl;
          if( !head )
          {
                head = new Card( rank, suit );
                continue;
          }
          tmp = new Card( rank, suit );
          if( !Sort( head, tmp ) ) 
              check = false;
      }
      if( check )
        cout << "YES" << endl;
      else
        cout << "NO" << endl;
    }
    return 0;
}