min_x = 0
max_x = 10**9
correct = false
10.times do
	x = (max_x - min_x) / 2 + min_x
	print "? #{x}\n"
	STDOUT.flush
	y = gets.strip.to_i
	if y == 1
		max_x = (max_x - min_x) / 2 + min_x
	else
		min_x = (max_x - min_x) / 2 + min_x
	end
	if min_x == max_x
		break
	end
end
print "! #{min_x}\n"