#include <iostream>
#include <list>

using namespace std;

int decode(char c){
    if(c=='A') return 1;
    if(c=='X') return 10;
    if(c=='J') return 11;
    if(c=='Q') return 12;
    if(c=='K') return 13;

    if(c=='C') return 14;
    if(c=='D') return 15;
    if(c=='H') return 16;
    if(c=='S') return 17;

    return c-'0';
}

int visited[20];
list<int> data[20];

void dfs(int i){
    //cout << "DFS " << i << endl;
    if(visited[i] != 0) return;
    visited[i] = 1;
    for(int j : data[i])
        dfs(j);
}

int main()
{
    int N;
    while(cin >> N){
        for(int i=0; i<20; i++){
            data[i].clear();
            visited[i] = -1;
        }

        for(int i=0; i<N; i++){
            string s;
            cin >> s;
            int a = decode(s[0]);
            int b = decode(s[1]);
            //cout << s << ' '<< a << ' '<< b << endl;
            data[a].push_back(b);
            data[b].push_back(a);
            visited[a] = visited[b] = 0;
        }

        for(int i=0; i<20; i++){
            if(visited[i] == 0){
                dfs(i);
                break;
            }
        }

        bool ok = true;
        for(int i=0; i<20; i++){
            if(visited[i] == 0) {
                ok = false;
                break;
            }
        }

        cout << (ok ? "YES" : "NO") << endl;
    }
    return 0;
}