Equivalent Pairs

You are given a list of integers nums. Return the number of pairs i < j such that nums[i] = nums[j].

Constraints

• 0 ≤ n ≤ 100,000 where n is the length of nums

https://binarysearch.com/problems/Equivalent-Pairs

Examples

Example 1

Input

• nums = [3, 2, 3, 2, 2]

Output

• answer = 4

Explanation

We have index pairs (0, 2), (1, 3), (1, 4), (3, 4).

Solution