import sys

def compute_zeta(s):
    if s >= 54:
        return 1.0
    sum_z = 0.0
    k = 1
    while True:
        term = 1.0 / (k ** s)
        if term < 1e-20:
            break
        sum_z += term
        k += 1
    return sum_z

def main():
    N = int(sys.stdin.readline())
    s = N + 2
    zeta_value = compute_zeta(s)
    print("{0:.9f}".format(zeta_value))

if __name__ == "__main__":
    main()