#include <bits/stdc++.h> 
int pairSum(vector<int> &arr, int n, int target)
{
	int count=0;
	unordered_map<int,int>mp;
	for(int i=0 ; i<n ; i++)
	{
       if(mp.find(target-arr[i])!=mp.end())
	   {
		   count+=mp[target-arr[i]];
	   }
	   else
	   {
		   mp[arr[i]]++;
	   }
	}
	if(count==0)
	return -1;
	else
	return count;
}