#include <bits/stdc++.h>
using namespace std;

//判断字符串是否能够接龙 
bool fun(string s){
	string a[30],w="";
	int i,k = 0;
	for(i = 0;i < s.size();i++){
		if(s[i] != ' '){
			w = w + s[i];
			if(i == s.size() - 1 || s[i+1] == ' '){
				a[k] = w;
				if(k != 0 && a[k][0] != a[k-1][a[k-1].size()-1]){
					return false;
				}
				k++;
				w = "";
			}
		}
	}
	
	return true;
}

int main() {
	string s;
	getline(cin,s);
	if(fun(s)){
		cout<<"Y";
	}else{
		cout<<"N";
	}
}


/**************************************************************
	Problem: 1728
	User: admin
	Language: C++
	Result: Accepted
	Time:30 ms
	Memory:2080 kb
****************************************************************/