#include <iostream>
#include <string>
using namespace std;
int main(){
	int n;	cin>>n;
	string s;	cin>>s;
	for(int i=1;i<n;i++){
		if(s[i]==s[i-1]){
			cout<<"YES"<<endl;
			return 0;
		}
		else if(i+2<n){
			if(s[i-1]==s[i+1]&&s[i]==s[i+2]){
				cout<<"YES"<<endl;
				return 0;
			}
		}
	}
	cout<<"NO"<<endl;
	return 0;
}