import sys
input = sys.stdin.readline

N=int(input())
for i in range(0,N-1,2):
    j=i+1
    print("?",i,j,flush=True)
    x=int(input())

    if x==i:
        print("!",j,flush=True)
        break
    elif x==j:
        print("!",i,flush=True)
        break
else:
    print("!",N-1,flush=True)