def solve():
    def query(x):
        print('?', x)
        return True if input() == 'Yes' else False
    ng = 1222 * pow(10, 72) + 1
    ok = 0
    
    while True:
        if abs(ng - ok) / abs(ng) <= pow(10, -5):
            print('!', ok)
            break
        mid = (ok + ng) / 2
        if query(mid):
            ok = mid
        else:
            ng = mid

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