Given N, calculate

i.e. the sum of all N divided by i, rounded down, for all i from 1 to N.

Input

A positive integer N (N ≤ 10^12).

Output

The sum of all N divided by i, rounded down, for all i from 1 to N.

Example

Input:
4

Output:
8

Input:
10

Output:
27

Input:
32

Output:
119