Matching Gift Cards

Story

The corner shop sells gift cards of many different values. Every evening the cashier pairs up the leftover cards so that each pair is worth exactly the price of the monthly special. How many different pairs can she make?

Task

You are given the values of n cards and a target T. Count the pairs of cards (i, j) with i < j and a[i] + a[j] = T.

Two cards with the same value at different positions are different cards, and a card can never be paired with itself.

Input

• Line 1: n and T
• Line 2: n integers a[1] … a[n]

Limits: 1 ≤ n ≤ 10 000, |a[i]| ≤ 10^9, |T| ≤ 2·10^9. Checking all n²/2 pairs is too slow on the largest tests; aim for one pass over the list.

Output

One integer: the number of pairs.

Example

6 10
3 7 5 5 5 2

Output: 4, because 3 + 7 is one pair and the three 5s give 5 + 5 in three different ways.

6 10
3 7 5 5 5 2