line1 = gets.chomp!
abort "line1" unless line1 =~ /^[0-9]+$/
n = line1.to_i
abort "n" unless 1 <= n && n <= 20000
hh = {}
n.times do |i|
  line = gets.chomp!
  abort "no.#{i}" unless line =~ /^[A-Za-z]+ [A-Za-z]+$/
  a, b = line.split
  abort "twice badman" if hh[a]
  hh[a] = true
end
abort "EOF" if gets
puts 'AC!'