#N = 5
#D = 2

def make_divisors(n):
    divisors = []  #必要に応じてsetにしても良いかも
    i = 1
    while i ** 2 <= n:
        if n % i == 0:
            divisors.append(i)
            if i ** 2 != n:
                divisors.append(n//i)
        i += 1
    divisors.sort()
    return divisors

def check(x):
     print("?",x)
     return input() == "safe"
    # return x < N and x % D != 0

def search(lb,d):
    ub = 1000
    while ub - lb > 1:
        mid = (ub + lb) // 2
        if mid % d == 0:
            mid += 1
        if check(mid):
            lb = mid
        else:
            ub = mid
    return lb

x = search(0,1000)
if check(x+2):
    DL = make_divisors(x)
    for i in DL:
        if check(i):
            continue
        else:
            break
    y = search(x+2,i)
    print(y)
else:
    print(x)