import sys
ok = 1
ng = 10**9 + 1
while abs(ok - ng) > 1:
    mid = (ok + ng) // 2
    print("? %d" % mid)
    sys.stdout.flush()
    query = int(input())
    if query:   # x >= mid
        ok = mid
    else:
        ng = mid
print("! %d" % ok)
sys.stdout.flush()