rmin = 1
rmax = 10 ** 9
while rmin < rmax do
    mid = (rmin + rmax) / 2
    print "? ", mid, "\n"
    STDOUT.flush
    if gets.to_i == 1
        rmin = mid
    else
        rmax = mid - 1
    end
end
print "! ", rmin, "\n"
STDOUT.flush