#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <set>
using namespace std;

int main(){
	int n;
	cin >> n;
	bool ok = n>3;
	if(ok){
		cout << "YES" << endl;
		return 0;
	}

	string s;
	cin >> s;
	for(int i=0; i<n-1; i++){
		if(s[i] == s[i+1]) ok = true;
	}

	cout << (ok?"YES" : "NO") << endl;
	return 0;
}