Pair Sum Problem Statement

You are provided with an array ARR consisting of N distinct integers in ascending order and an integer TARGET. Your objective is to count all the distinct pairs in ARR whose sum equals TARGET.

Note:

• Pair (x, y) and Pair (y, x) are considered as the same pair.
• If no such pair exists with a sum equal to 'TARGET', then return -1.

Example:

Input:

ARR = [1, 2, 3], TARGET = 4

Output:

1

Explanation:

There exists only one pair in ARR with a sum of 4, which is (1, 3). (1, 3) and (3, 1) are counted as a single pair.

Constraints:

• 1 ≤ T ≤ 100
• 2 ≤ N ≤ 5000
• 1 ≤ ARR[i], TARGET ≤ 105
• The array ARR contains distinct elements.