import sys

ok = 1
ng = 10 ** 9 + 1
while abs(ok - ng) > 1:
  mid = (ok + ng) // 2
  print(f"? {mid}")
  sys.stdout.flush()
  res = int(input())
  if res == 1:
    ok = mid
  else:
    ng = mid

print(f"! {ok}")
sys.stdout.flush()