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.
10
3
20
5