#include <bits/stdc++.h>
using namespace std;
vector< vector<int> > G;
bool vis[100];
void dfs(int u, int p){
    if(vis[u]) return;
    vis[u] = 1;
    for(int v : G[u])
        dfs(v, u);
}


void process(int n){
    vector<pair<int, int> > v;
    for(int i = 0; i < n; i++){
        string s; cin >> s;
        v.push_back({s[0], s[1]});
    }
    G = vector< vector<int> >(n);
    for(int i = 0; i < n; i++)
        for(int j = i+1; j < n; j ++)
            if(v[i].first == v[j].first
            || v[i].second == v[j].second){
                G[i].push_back(j);
                G[j].push_back(i);
            }
    memset(vis, 0, sizeof(vis));
    dfs(0, -1);
    bool isCon = true;
    for(int i = 0; i < n; i ++)
        if(!vis[i])
            isCon = false;
    isCon? puts("YES")
         : puts("NO");
}

int main ()
{
    int n;
    while(cin >> n){
        process(n);
    }
}