# SumX

Very easy

Execution time limit is 1 second

Runtime memory usage limit is 128 megabytes

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

Input #1

Answer #1

Input #2

Answer #2

Submissions 377

Acceptance rate 36%