import math

N = int(input())
if N < 10:
    print(1.0)
else:
    eps = 1e-12
    denominator = eps * (N - 1)
    if denominator <= 0:
        M = 2
    else:
        rhs = 1.0 / denominator
        expo = 1.0 / (N - 1)
        nupper = rhs ** expo
        M_minus_1 = math.ceil(nupper)
        M = M_minus_1 + 1

    total = 0.0
    for i in range(1, M + 1):
        term = math.exp(-N * math.log(i))
        total += term

    # Formatting the output to handle trailing zeros and decimal points
    formatted_total = "{0:.16f}".format(total)
    if '.' in formatted_total:
        formatted_total = formatted_total.rstrip('0').rstrip('.')
    print(formatted_total)