# frozen_string_literal: true

def solve
  solve_ ? 'YES' : 'NO'
end

def solve_
  case N
  when 1 then false
  when 2 then S[0] == S[1]
  when 3 then S[0] == S[1] || S[1] == S[2]
  else true
  end
end

N = gets.to_i
S = gets.chomp

puts solve