import sys

n = int(input())

for i in range(n//2):
    x,y = 2*i,2*i+1
    print("?",x,y)
    sys.stdout.flush()

    z = int(input())
    if z == x:
        print("!",y)
        sys.stdout.flush()
        exit()
    if z == y:
        print("!",x)
        sys.stdout.flush()
        exit()
print("!",n-1)
sys.stdout.flush()

exit()