Problem Statement

You are given a positive integer N.
Find the number of quadruples of positive integers (A,B,C,D) such that AB + CD = N.
Under the constraints of this problem, it can be proved that the answer is at most $9 \times 10^{18}$.

Input

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

Output

Print the answer.

Constraints

• $2 \leq N \leq 2 \times 10^5$
• N is an integer.

Sample Input 1

4

Sample Output 1

8

Here are the eight desired quadruples.

• (A,B,C,D)=(1,1,1,3)
• (A,B,C,D)=(1,1,3,1)
• (A,B,C,D)=(1,2,1,2)
• (A,B,C,D)=(1,2,2,1)
• (A,B,C,D)=(1,3,1,1)
• (A,B,C,D)=(2,1,1,2)
• (A,B,C,D)=(2,1,2,1)
• (A,B,C,D)=(3,1,1,1)

Sample Input 2

292

Sample Output 2

10886

Sample Input 3

19876

Sample Output 3

2219958

见题面 Input 部分

见题面 Output 部分