import math
from decimal import *
getcontext().prec = 200

def query(y):
    print('? {:.20f}'.format(y), flush=True)
    s = input()
    assert(s != "-1")
    return s == "Yes"

def solve():
    Q = 24
    if query(Decimal(262144) / 3125):
        lb = Decimal(0)
        ub = Decimal(262144) / 3125
        for _ in range(1, Q):
            mid = (lb + ub) / 2
            if query(mid):
                ub = mid
            else:
                lb = mid
        print('! {:.20f}'.format((lb + ub) / 2), flush=True)
    else:
        lb = Decimal(262144) / 3125
        ub = Decimal(1222) * (Decimal(10) ** 72)
        for _ in range(1, Q):
            mid = (lb * ub).sqrt()
            if query(mid):
                ub = mid
            else:
                lb = mid
        print('! {:.20f}'.format(2 * lb * ub / (lb + ub)), flush=True)

t = int(input())
for _ in range(t):
    solve()