N = int(input())
flag = False
for i in range(N//2):
    print("?",2*i,2*i+1)
    z = int(input())
    if z==2*i:
        print("!",2*i+1)
        flag = True
        break
    elif z==2*i+1:
        print("!",2*i)
        flag = True
        break
if not flag:
    print("!",N-1)