76分求调，必关

**#include<cmath>
#include<bits/stdc++.h>
using namespace std;
long long n,c,a[20003],b,l,r,mid,cs,x1,x2;
bool cmp(int x,int y){
	return x<y;
}
int main()
{
	cin>>n>>c;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	sort(a+1,a+1+n,cmp);
	for(int i=1;i<=n;i++){
		b=a[i]+c;
		l=i+1;
		r=n;
		while(l<=r){//找最靠前 
			mid=(l+r)/2;
			if(b<=a[mid]){
				//x1=mid;
				r=mid-1;
			}
			else if(b>a[mid]){
				l=mid+1;
			}
		}
		x1=l;
		l=i+1;
		r=n;
		while(l<=r){//找最靠后 
			mid=(l+r)/2;
			if(b>=a[mid]){
				//x2=mid;
				l=mid+1;
			}
			else {
				r=mid-1;
			}
		}
		x2=l;
		cs=cs+(x2-x1);
	}
	cout<<cs;
	return 0;
}