def main
  while num = gets
    num = num.chomp.to_i
    break if num == 0
    arr = gets.chomp.split(/\s/).collect { |x| x.to_i}
    arr = arr.each_slice(2).to_a.delete_if { |x| x.size == 2 and x[0] != x[1]}
    if arr.empty?
      puts "NO COLOR"
    else
      puts arr[0][0]
    end 
  end
end

main