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

#define rep(i,n) for(int i=0;i<n;i++)

int main(){
	string eto[12]={"ne", "ushi", "tora", "u", "tatsu","mi","uma","hitsuji","saru","tori","inu","i"};
	string diff[12];
	string ans, cnt;
	int exec=0;
	int n;
	cin>>n;
	
	rep(i,n){
		cin>>diff[i];
	}
	rep(i,n){
		diff[i]=cnt;
		if(cnt==diff[i+1]) exec++;
	}
	if(exec==1){
		cout<<"NO"<<endl;
	}else{
		cout<<"YES"<<endl;
	}
	return 0;
}