#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int N;
  cin >> N;
  string S;
  cin >> S;
  for (int i = 0; i < N - 1; i++) {
    if (S[i] == S[i + 1]) {
      cout << "YES" << '\n';
      return 0;
    }
  }
  for (int i = 0; i < N - 3; i++) {
    if (S[i] == S[i + 2] && S[i + 1] == S[i + 3]) {
      cout << "YES" << '\n';
      return 0;
    }
  }
  cout << "NO" << '\n';
  return 0;
}