Preparing NOJ

Coprime

1000ms 262144K

Description:

Suppose you are exploring how to split a positive integer n into the sum of two positive integers $$$i,j$$$, and $$$gcd(i,j)=1$$$. You want to know how many pairs $$$(i,j)$$$ that can meet the conditions. It's so easy, so you need to calculate the sum of number of pairs when n ranges from 1 to N.

Please note that we think $$$(i,j)$$$ and $$$(j,i)$$$ are different, when $$$i\neq j$$$.

Input:

The first line of the input is a positive integer N$$$(2\leq N\leq 10^5)$$$

Output:

One integer denotes the number of pairs $$$(i,j)$$$

Sample Input:

2

Sample Output:

1

Info

NOJ

Provider NOJ

Code NOJ2376

Tags

Submitted 297

Passed 82

AC Rate 27.61%

Date 08/13/2019 00:47:12

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