N = int(input())
for i in range(N//2):
  print('?',2*i,2*i+1)
  a = int(input())
  if a == 2*i:
    print('!',2*i+1)
    exit()
  elif a == 2*i+1:
    print('!',2*i)
    exit()
print('!',N-1)
exit()