def f(d,u)
	if d==u then
		puts ["!",d]*" "
		STDIN.flush
	else
		m=(d+u)/2
		puts ["?",m]*" "
		STDIN.flush
		x=gets.to_i
		if x==1 then
			puts ["?",m+1]*" "
			STDIN.flush
			if gets.to_i==0 then
				puts ["!",m]*" "
				STDIN.flush
				return 
			end
		end
		if x==0 then
			f(d,m)
		else
			f(m+1,u)
		end
	end
end
f(1,10**9)