l = 10
r = 1000000001
c = 0
loop{
    y = (l + r) / 2
    puts "? #{y}"
    STDOUT.flush
    ans = gets.to_i
    if ans == 0
        puts "! #{y + c}"
        STDOUT.flush
        break
    elsif ans > 0
        l = y
    else
        r = y
    end
    #r = [r - 1,0].max
    l = [l - 1,0].max
    c += 1
    }