STDOUT.sync = true

def binary_search(min, sup, count = 0)
	while sup - min > 1
		mid = (min + sup) / 2
		puts "? #{mid - count}"
		case gets.to_i
		when 0
			puts "! #{mid}"
			exit
		when -1
			sup = mid
		when 1
			min = mid + 1
		end
        count += 1
	end
    puts "! #{min}"
    exit
end

THRESH = 100
puts "? #{THRESH}"
case gets.to_i
when -1
	binary_search(10, THRESH, 1)
when 1
	binary_search(THRESH + 1, 10**9 + 1, 1)
when 0
	puts "! #{THRESH}"
end