import sys
input = sys.stdin.readline

N = int(input())
for i in range(N//2):
    x = 2*i
    y = x+1
    print('?', x, y, flush=True)
    z = int(input())
    if z == x or z == y:
        print('!', z ^ 1, flush=True)
        exit()
print('!', N-1, flush=True)