n= int(input())

for i in range(n//2):
    print("?", 2*i, 2*i+1)
    z = int(input())
    if z == 2*i:
        print("!",2*i+1)
        break
    elif z == 2*i+1:
        print("!",2*i)
        break
else:
    print("!",n-1)