from math import sqrt
from sys import stdout


def query(s: str) -> str:
    print("?", s)
    stdout.flush()
    res = input().rstrip()
    if res == "-1":
        exit(0)
    return res == "Yes"


def answer(s: str):
    print("!", s)
    stdout.flush()


def float2string(f: float) -> str:
    s = f"{f:0.100f}"
    return s[0] + s[1:].rstrip("0").rstrip(".")


def middle(left: float, right: float, last=False) -> float:
    if last:
        return 2 * right * left / (right + left)
    else:
        return sqrt(left * right)


def solve():
    left = 1e-6
    right = 12.22e74
    for _ in range(24):
        mid = middle(left, right)
        if query(float2string(mid)):
            left = mid
        else:
            right = mid
    return answer(float2string(middle(left, right, True)))


def main():
    T = int(input())
    for _ in range(T):
        solve()


if __name__ == "__main__":
    main()