import sys

int1 = lambda x: int(x) - 1

# input = lambda: sys.stdin.buffer.readline()
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
i1 = lambda: int1(input())
mi = lambda: map(int, input().split())
mi1 = lambda: map(int1, input().split())
li = lambda: list(mi())
li1 = lambda: list(mi1())
lli = lambda n: [li() for _ in range(n)]

INF = float("inf")
# mod = int(1e9 + 7)
mod = 998244353

n = ii()
for x in range(0, n - 1, 2):
    y = x + 1
    print("?", x, y)
    sys.stdout.flush()
    z = ii()
    if z == x:
        print("!", y)
        sys.stdout.flush()
        exit()
    if z == y:
        print("!", x)
        sys.stdout.flush()
        exit()
print("!", n - 1)
sys.stdout.flush()