#include <bits/stdc++.h>
#define GET_MACRO(a, b, c, NAME, ...) NAME
#define rep(...) GET_MACRO(__VA_ARGS__, rep3, rep2)(__VA_ARGS__)
#define rep2(i, a) rep3 (i, 0, a)
#define rep3(i, a, b) for (int i = (a); i < (b); i++)
#define repr(...) GET_MACRO(__VA_ARGS__, repr3, repr2)(__VA_ARGS__)
#define repr2(i, a) repr3 (i, 0, a)
#define repr3(i, a, b) for (int i = (b) - 1; i >= (a); i--)
#define chmin(a, b) ((b) < a && (a = (b), true))
#define chmax(a, b) (a < (b) && (a = (b), true))
using namespace std;
typedef long long ll;

bool check(string s) {
	int n = s.length();
	rep (i, n - 1) {
		if (s[i] == s[i + 1]) return true;
	}
	if (n <= 3) return false;
	return true;
}

int main() {
	int N;
	string S;
	cin >> N >> S;
	if (check(S)) {
		cout << "YES" << endl;
	} else {
		cout << "NO" << endl;
	}
	return 0;
}