from fractions import Fraction
def out(x, y):
    fu = x < 0
    x = str(abs(x))
    ans = "0." + "0" * (y - len(x) - 1) + x
    if fu:
        ans = "-" + ans
    return ans
n = int(input())
if n > 0:
    print(0)
elif n < 0:
    n *= -1
    a = [Fraction(0) for i in range(n + 1)]
    a[0] = Fraction(1, 10)
    a[1] = Fraction(-1, 100)
    for i in range(2, n + 1):
        a[i] = -(a[i - 1] + a[i - 2]) / 10
    print(out(a[n].numerator, len(str(a[n].denominator))))
else:
    print("0.1")