Bzoj 2818: GCD pull function

2818: gcdtime limit: 10 sec memory limit: 256 MB
Submit: 1633 solved: 724
[Submit] [Status] Description

Given the integer N, evaluate 1 <= X, Y <= N and gcd (x, y) as the prime number
Number of (x, y) pairs.

 

Input

An integer n

Output

Example

Sample input4

Sample output4hint

 

Hint

For example (2, 2), (2, 4), (3, 3), (4, 2)

1 <= n <= 10 ^ 7

 

Source

Calculate the gcd (x, y) = prime [k] logarithm (1 <= X, Y <= N)

Calculate GCD (x, y) = 1, (1 <= X, Y <= N/P)

Set SPHI (k) to indicate gcd (x, y) = 1, (1 <= X, Y <= K), then, the SPHI (K) = PHI (k) * 2 + SPHI (k-1) can be pushed through the probe method)

Then this problem can be solved.

 

Bzoj 2818: GCD pull function