n = int(input())
now = 0
while True:
	print(f"? {now + 1} {now + 2}")
	x = int(input())
	if x == now + 1:
		print(f"! {now + 2}")
		exit()
	if x == now + 2:
		print(f"! {now + 1}")
		exit()
	if now == n-1:
		print(f"! {n}")
		exit()
	now += 2