Inverted GCD

4.4

14 votes
Medium-Hard
Problem

Given an array a of N numbers , you have to find the number of pair of indices i and j that satisfy the following relation:
1. i < j
2. ai > aj
3. gcd( ai , aj )=1

Input
The first line of the input contains a single integer N - denoting the size of the array.
The next line contains N space separated integers denoting the array a.

Output
Output a single integer - the answer to the problem stated above.

Constraints
1<=N<=105
1<=ai<=105

Time Limit: 2
Memory Limit: 256
Source Limit:
Explanation

The indices that satisfy the given condition are (1,4) , (2,4) and (3,4).

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