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)
        break
    elif a == 2 * i + 1:
        print("!", 2 * i)
        break
else:
    print("!", N - 1)