import sys
from collections import deque, Counter
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 63 - 1
mod = 998244353

def query(x, y):
    print('?', x, y, flush=True)
    return ii()

def answer(z):
    print('!', z, flush=True)
    exit()


n = ii()
s = set(range(n))
pos = {}
for i in range(n):
    if i not in s:
        continue
    s.discard(i)
    z = query(i, i)
    if z == i:
        answer(z)
    if z in pos and n % 2 == 0:
        answer(pos[z])
    
    s.discard(z)
    if len(s) == 1:
        answer(s.pop())
    pos[i] = z