Problem Statement

You are given a positive integer N.
Find the number of triples of positive integers (A, B, C) such that $A\leq B\leq C$ and $ABC\leq N$.
The Constraints guarantee that the answer is less than 2^{63}.

Input

Input is given from Standard Input in the following format:
N

Output

Print the answer.

Constraints

• $1 \leq N \leq 10^{11}$
• N is an integer.

Sample Input 1

4

Sample Output 1

5

There are five such triples: (1,1,1),(1,1,2),(1,1,3),(1,1,4),(1,2,2).

Sample Input 2

100

Sample Output 2

323

Sample Input 3

100000000000

Sample Output 3

5745290566750

见题面 Input 部分

见题面 Output 部分