#include <iostream>
#include <vector>
#include <deque>
#include <string>
using namespace std;
struct Graph{
	int v;
	int e;
	vector<vector<int>> adj;
	vector<bool> visited;
	
	Graph(int _v) : v(_v) {
		adj.resize(v);
		visited.assign(v, false);
	}
	bool validateV(int _v){
		return ( _v >= 0 && _v < v);
	}
	void insert(int _a, int _b){
		if(!validateV(_a) || !validateV(_b)) return;
		
		adj[_a].push_back(_b);
	}
	int degree(int _v){
		if(!validateV(_v)) return 0;
		return outDegree(_v) + inDegree(_v);
	}
	int outDegree(int _v){
		if(!validateV(_v)) return 0;
		return adj[_v].size();
	}
	int inDegree(int _v){
		if(!validateV(_v)) return 0;
		int js = 0;
		for(auto x : adj){
			for(int i = 0; i < x.size(); i++){
				if(x[i] == _v) js++;
			}
		}
		return js;
	}
	void dfs(int _v){
		if(!validateV(_v)) return;
		if(visited[_v]) return;
		visited[_v] = true;
		for(auto x : adj[_v]){
			dfs(x);
		}
	}
	bool isConnected(){
		dfs(0);
		for(auto x : visited){
			if(!x) return false;
		}
		
		int js = 0;
		for(int i = 0; i < v; i++){
			if(degree(i) % 2 == 1) js++;
		}
		return (js == 0) || (js == 2);
	}
};
int main(){
	int n;
	cin >> n;
	Graph g(n);
	vector<string> s;
	s.resize(n);
	for(int i = 0; i < n; i++){
		cin >> s[i];
	}
	for(int i = 0; i < n; i++){
		for(int j = 0; j < n; j++){
			if(i != j && s[i].back() == s[j].front()) g.insert(i, j);
		}
	}
	g.isConnected() ? cout << "YES" << endl : cout << "NO" << endl;
	system("pause");
	return 0;
}