l = 1
h = 10 ** 9
a = -1

100.times {
    a = (l + h).div(2)
    puts "? #{a}"
    ans = gets.to_i
    if ans == 1
        l = a
    else
        h = a
    end
    
    break if l == h
}
if l == h
    puts "! #{l}"
else
    a = (l .. h).to_a.sample
    puts "! #{a}"
end