//https://ncode.syosetu.com/n4830bu/290/
#include <bits/stdc++.h>
using namespace std;

int main() {
    int N;
    string S;
    cin >> N >> S;
    cout << (N >= 4 || S[0] == S[1] || (N == 3 && S[1] == S[2]) ? "YES" : "NO") << endl;
}