#include <stdio.h>
#include <iostream>
#include <vector>
#include <set>
#include <string>
#include <map>
#include <algorithm>

using namespace std;

int find_etalon(vector<string> arr){
    if(arr[0]==arr[1])
        return 0;
    if(arr[0]==arr[2])
        return 0;
    if(arr[1]==arr[2])
        return 1;
}

bool ans;

bool dfs(map<char,set<char>> st, char v){
    if(ans)
        return true;
    if(st.size()==1)
        return true;
    set<char> paths = st[v];
    st.erase(v);
    for(auto i=paths.begin();i!=paths.end();i++){
        for(auto el: st){
            if(el.second.find(*i)!=el.second.end()){
                map<char,set<char>> nst(st);
                if(el.second.size()>1)
                    nst[el.first].erase(*i);
                //cout << v << el.first << " " << nst.size() <<endl;
                ans |= dfs(st,el.first);
            }
        }
    }
    return ans;
}

int main(){
    //freopen("input.txt","r",stdin); freopen("output.txt","w",stdout);
    int n;
    while(cin>>n){
        map<char,set<char>> suits, ranks;
        for(int i=0;i<n;i++){
            string s;
            cin >> s;
            ranks[s[0]].insert(s[1]);
            suits[s[1]].insert(s[0]);
        }
        ans = false;
        for(auto el:ranks){
            ans |=dfs(ranks,el.first);
        }
        for(auto el:suits){
            ans |=dfs(suits,el.first);
        }
        string san = (ans)?"YES":"NO";
        cout << san << endl;
    }
    return 0;
}