A "Special Number" is defined as a positive integer that has exactly three distinct positive divisors.
Given an integer M, your task is to find the number of "Special Numbers" in the range [1, M].
Input
The input contains a single integer M (1 \le M \le 10^{15}).
Output
Print a single integer — the count of "Special Numbers" n such that 1 \le n \le M.
Examples
| standard input | standard output |
|---|
| 10
| 2
|
| 25
| 3
|