n = 500000000
d = 500000000
pre = "1\n"
while d > 0
	puts "? " + n.to_s
	if gets == "1\n"
		d /= 2 if pre != $_
		n += d
	else
		d /= 2 if pre != $_
		n -= d
	end
	pre = $_
end
puts "! " + (n-1).to_s