#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
int main() {
	int n;
	string s;
	cin >> n >> s;
	bool b = false;
	for (int i = 0; i < n - 1; i++) {
		if (s[i] == s[i + 1]) {
			b = true;
		}
	}
	if (b || n >= 4) {
		cout << "YES" << endl;
	}
	else {
		cout << "NO" << endl;
	}
}