import sys
min = 1
max = 1000000000

while min != max:
    y = (min + max) // 2
    print("? %d" % y)
    sys.stdout.flush()
    a = input()
    if a == "1":
        min = y
    else:
        max = y - 1

print("! %d" % min)
sys.stdout.flush()