C++

#include <bits/stdc++.h>
using namespace std;
int a[200010],n,c,cnt=0;
int main(){
cin >> n >> c;
for (int i=1;i<=n;i++){
cin >> a[i];
}
sort (a+1,a+n+1);
for (int i=1;i<=n;i++){
int x=a[i]-c;
int p1=upper_bound (a+1,a+n+1,x)-a;
int p2=lower_bound (a+1,a+n+1,x)-a;
cnt+=p1-p2;
}
cout << cnt;
return 0;
}