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

class CARD
{
public:
    char m_Rank;
    char m_Color;
    CARD(const char & rank, const char & color):
    m_Rank(rank),m_Color(color){}
    friend bool operator<(CARD x, CARD y)
    {
        if(x.m_Color == y.m_Color)
            return x.m_Rank < y.m_Rank;
        else
            return x.m_Color < y.m_Color; 
    }
    friend bool operator ==(CARD x, CARD y)
    {
        return x.m_Color == y.m_Color or x.m_Rank == y.m_Rank;
    }
};


int main(int argc, char** argv) {
    size_t cnt = 0;
    char color = 0;
    char rank = 0;
    bool isError = false;
    while(cin >> cnt)
    {
        set<CARD> karty;
        for(size_t i = 0; i < cnt; i ++)
        {
            cin >> ws >> rank >> color;
            karty.insert(CARD(rank,color));
        }
        for(set<CARD>::iterator it = karty.begin(); it != karty.end(); it++)
        {
            if(*it == *(it++)) continue;
            isError = true;
            break;
        }
        if(isError) cout << "NO" << endl;
        else cout << "YES" << endl;
        isError = false;
    }
    
    return 0;
}