Four Divisors

10000ms

786432K

Description:

If an integer a is divisible by another integer b, then b is called the divisor of a.

For example: 12 has positive 6 divisors. They are 1, 2, 3, 4, 6 and 12.

Let’s define a function D(n) — number of integers between 1 and n (inclusive) which has exactly four positive divisors.

Between 1 and 10 only the integers 6, 8 and 10 has exactly four positive divisors. So, D(10) = 3.

You are given an integer n. You have to calculate D(n).

The only line contains integer n (1 ≤ n ≤ 10¹¹) — the parameter from the problem statement.

Print the only integer c — the number of integers between 1 and n with exactly four divisors.

Informação

Provedor Codeforces

Código CF665F