#include<bits/stdc++.h>
using namespace std;

int findPairOfDifference(long long arr[],long long n,long long k){
     long long  i=0,j=1,cnt=0;
     while(i<n && j<n){
        if(i!=j && arr[j]-arr[i]==k){
            cnt++;
           //cout<<"arr[j]="<<arr[j]<<" "<<"arr[i]="<<arr[i]<<endl;
            j++;
        }
        else if(arr[j]-arr[i]<k){
                //cout<<"sum="<<arr[j]-arr[i]<<endl;
            j++;
        }
        else{
            i++;
        }
     }
     return cnt;

}
int main(){
    long long n,i,k;
    cin>>n;
    long long arr[n];
    for(i=0;i<n;i++){
        cin>>arr[i];
    }
    cin>>k;
    sort(arr,arr+n);
    int result=findPairOfDifference(arr,n,k);
    cout<<result*2<<endl;
    return 0;
}