SumX

Consider an array of n positive integers a[1], a[2], ..., a[n], having values between 1 and 10^6 and an integer x. Write a program to determine the number of pairs (a[i], a[j]), where 1 ≤ i < j ≤ n and a[i] + a[j] = x.

Input

The first line contains the integer n (1 ≤ n ≤ 10^5). The second line contains n integers - the elements of array that can be repeated. On the third line the integer x (1 ≤ x ≤ 2 * 10^6) is given.

Output

Print the calculated number of pairs.

Examples