N = int(input())
import sys

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