min = 1
max = 10**9
while max - min != 1
  puts "? #{(max + min)/2}"
  STDOUT.flush
  ans = gets.to_i
  case ans
  when 0
    max = (max + min)/2 - 1
  when 1
    min = (max + min)/2
  end
end
puts "? #{max}"
STDOUT.flush
ans = gets.to_i
case ans
when 0
  puts "! #{min}"
when 1
  puts "! #{max}"
end