package stonehee.baekjoon;

import java.io.BufferedReader;

import java.io.IOException;

import java.util.Arrays;

public class SumForTwoNum {

public static void main(String[] args) throws IOException {

BufferedReader br = new BufferedReader(new java.io.InputStreamReader(System.in));

int arrLen = Integer.parseInt(br.readLine());

int[] arr = Arrays.stream(br.readLine().split(" "))

.mapToInt(Integer::parseInt)

.toArray();

int x = Integer.parseInt(br.readLine());

System.out.println(findPair(arr, x));

}

private static int findPair(int[] arr, int x) {

Arrays.parallelSort(arr);

int cnt = 0;

int start = 0;

int end = arr.length - 1;

int sum = 0;

while(start < end) {

sum = arr[start] + arr[end];

if(sum == x) cnt++;

if(sum <= x) start++;

else end--;

}

return cnt;

}

}