def f(n):
    t = []
    for i in range(2, 10 ** 3):
        x = i ** n
        if x > 1000000000:
            break
        t.append(1000000 / x)
    return sum(t)

x = int(input())

result = 1000000
for i in range(3, x):
    result -= f(i)
print(result)