You have been given an integer array/list(arr) and a number 'Sum'. Find and return the total number of pairs in the array/list which when added, results equal to the 'Sum'.
Given array/list can contain duplicate elements.
(arr[i],arr[j]) and (arr[j],arr[i]) are considered same.
Input format :
The first line contains 2 space-separated integers N and Sum.
The next line contains N space-separated integers representing array elements.
Output format :
Print the total number of pairs present in the array/list.
1 <= N <= 10^5
-10^4 <= Sum <= 10^4
-10^4 <= arr[ i ] <= 10^4
Time Limit: 1 sec