import re
import sys

content = input()
pattern = r'^(\d+)$'
result = re.match(pattern, content)

if not result:
    sys.exit("format error.")

T = int(content)

if not (1 <= T and T <= 10**5):
    sys.exit("T")

for _ in range(T):
    content = input()
    pattern = r'^(\d+) (-?0.\d{5})$'
    result = re.match(pattern, content)

    if not result:
        sys.exit("format error.")

    n, x = content.split()
    n = int(n)
    x = float(x)

    if not (0 <= n and n <= 10**5):
        sys.exit("N")

    res = ((x - 1j)**(-n-1) - (x + 1j)**(-n-1)) * (-1)**n / 2j
    res *= (x**2 + 1)**(n/2 + 1)
    print(res.real)