二分的神

#include<iostream>
#include<algorithm>
using namespace std;
int main(){
    int n,c;
    cin>>n>>c;
    int a[200005];
    for(int i = 1;i<=n;i++){
        cin>>a[i];
    }
    sort(a+1,a+n+1);
    int sum=0;
    for(int i = 1;i<=n;i++){
        sum+=upper_bound(a+1,a+n+1,a[i]+c)-lower_bound(a+1,a+n+1,a[i]+c);
    }
    cout<<sum;
}