import sys

def main():
    N = int(sys.stdin.readline())

    print(f"? 0 1")
    sys.stdout.flush()
    p01 = int(sys.stdin.readline())
    if p01 == -1:
        return
    print(f"? 0 2")
    sys.stdout.flush()
    p02 = int(sys.stdin.readline())
    if p02 == -1:
        return
    print("! -1")

if __name__ == "__main__":
    main()