left   = 1
right  = 1000000000
target = (left + right ) / 2
puts "?#{target}"

unless left == right
        STDOUT.flush
        respons = gets.to_i
        if respons == 1 then
                left = target
                target = (left + right ) / 2
        else
                right = target
                target = (left + right ) / 2
        end
        puts "?#{target}"
end

puts "!#{target}"