题目描述
Problem Description
PJY came across a problem in a magazine:
Find all positive integer triplets {a, b, c} such that a, b, c ≤ n, the greatest common divisor of a, b, and c is 1, and 1/a + 1/b = 1/c.
PJY found this problem too easy and passed it on to LJJ, who loves counting. PJY also added the constraint n ≤ 1e12 and asked LJJ to count the number of such triplets {a, b, c}.
Note that when a is not equal to b, {a, b, c} and {b, a, c} are considered different triplets and should be counted twice.
LJJ got overwhelmed by the large number of triplets and passed the problem to you. Please output the count of such triplets.
Input Format
The input consists of a single line containing a positive integer n (n ≤ 1e12).
Output Format
The output consists of a single line containing an integer, representing the number of triplets {a, b, c} that satisfy the conditions.
Sample Input and Output
Sample Input #1
10
Sample Output #1
3
Sample Input #2
100
Sample Output #2
43
Sample Input #3
100000
Sample Output #3
42139
Notes/Hints
20%: n ≤ 2000
40%: n ≤ 100000
60%: n ≤ 10000000
80%: n ≤ 1e9
100%: n ≤ 1e12
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分