import math
n=int(input())
p=[]
for i in range(2,n+1):
    for j in range(2,i):
        if i%j==0:
            break
    else:
        p.append(i)
now=0
num=1
num2=1
cnt=0
while now!=len(p) and cnt<=450:
    tem=1
    while now!=len(p):
        if tem*p[now]>n:
            break
        tem*=p[now]
        now+=1
    cnt+=1
    print("?",tem,flush=True)
    k=int(input())
    num*=k
    num2*=tem//k
ans=num
for i in range((n//num),-1,-1):
    if math.gcd(num2,i)==1:
        print("?",num*i,flush=True)
        ans=max(ans,int(input()))
print("!",ans,flush=True)