Sam is amused by numbers so his friend gives him a puzzle to work upon. 
The puzzle is simple, given an array of N numbers, you have to find the number of unordered pairs with a sum of K. (These pairs need not be distinct)
Help Sam solve this puzzle for his friend.

INPUT:
The first line of input contains an integer N (the size of array) followed by N space seperated integers A[i]. 

The next line contains an integer K

OUTPUT:
Print the number of pairs with sum K

CONSTRAINTS:
1≤N≤10⁶

1≤A[i]≤10⁵

1≤K≤10⁵