min_x = 0
max_x = 10**9
ans = 140
100.times do
	x = (max_x - min_x) / 2 + min_x
	print "? #{x}\n"
	#print "? #{x}   #{min_x} #{max_x}\n"
	STDOUT.flush
	y = gets.strip.to_i
	#if x >= ans
	#	y = 1
	#else
	#	y = 0
	#end
	if y == 1
		max_x = x
	else
		min_x = x
	end
	if max_x - min_x == 1
		break
	end
end
print "! #{max_x}\n"