# Sumx

Consider a set of n distinct positive integers a_{1}, a_{2}, ..., a_{n}, having values between 1 and 1000000 and an integer x. Write a program sumx to determine the number of pairs (ai, aj), where 1 <= i < j <= n and ai + aj = x.

### Input

The first line of the standard input contains the integer n (1 <= n <= 100000). The second line contains n integers – the elements of the set. On the third line the integer x is given (1 <= x <= 2000000).

Remark: In 50% of test cases, n <= 1000.

### Output

The program should output on a single line of the standard output an integer – the calculated number of pairs.

### Constraints

Time limit: 1 second

Memory limit: 64 megabytes

### Examples

input 9 5 12 7 10 9 1 2 3 11 13 | output 3 |

Explanation: The different pairs with sum 13 are: (12, 1), (10, 3) and (2, 11).