n = gets.to_i

(n/2).times do |i|
  u = i*2
  v = i*2+1
  puts "? #{u} #{v}"
  STDOUT.flush
  w = gets.to_i
  if u == w
    puts "! #{v}"
    STDOUT.flush
    exit
  elsif v == w
    puts "! #{u}"
    STDOUT.flush
    exit
  end
end

puts "! #{n-1}"
STDOUT.flush