N = int(input())
def doubling(n, m):
    y = 1
    bas = n
    tmp = m
    while tmp:
        if tmp % 2:
            y *= bas
        bas *= bas
        tmp >>= 1
        if y == 0:
            break
    return y
S = 0
for i in range(1000000, 0, -1):
    S += doubling(1/i, N)
print(S)