#include <bits/stdc++.h>
#include <cstdint>
#include <sys/time.h>

typedef std::int_fast32_t  s32;
typedef std::uint_fast32_t u32;
typedef std::int_fast64_t  s64;
typedef std::uint_fast64_t u64;

const unsigned long mod = 1000000007;
const double EPS = 0.00000001;
const int INF = (1 << 29);

typedef std::pair<int, int> pii;

auto main() -> int
{

  int N;
  std::string str;

  std::cin >> N;
  std::cin >> str;

  bool b = false;
  if( str.size() <= 3 ) {
    for(int i = 0; i < str.size() - 1; ++i) {
      if( str[i] == str[i + 1] ) {
        b = true;
        break;
      }
    }
  }
  else {
    b = true;
  }

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