xxxxxxxxxx
#include <bits/stdc++.h>
using namespace std ;
typedef long long int ll ;
int main()
{
ll n ;
cin>>n ;
vector <ll> a ;
ll i = 0 ;
while(i<n)
{
ll x ;
cin>>x;
a.push_back(x);
i++;
}
map<pair<ll,ll>,ll> q ;
ll k ;
cin>>k ;
ll j = 0 ;
i = 0 ;
while(i<=n-1)
{
j = i + 1 ;
while(j<=n-1)
{
ll diff = abs(a[i]-a[j]);
if(diff==k)
{
ll x1 = min(a[i],a[j]);
ll y1 = max(a[i],a[j]);
q[{x1,y1}]++;
}
j++;
}
i++;
}
ll answer = q.size();
cout<<answer ;
return 0;
}