Guk

#include<stdio.h>
#include<algorithm>
using namespace std;
typedef long long int ll;

int main(){
    ll n;
    ll d;
    scanf("%lld %lld",&n,&d);
    ll arr[n+1];
    for(ll i = 1 ; i <= n ; i ++){
        scanf("%lld",&arr[i]);
    }
    sort(arr+1,arr+n+1);
/*  for(int i = 1 ; i <= n ; i++){
        printf("%d ",arr[i]);
    }printf("\n");*/
    ll i = 1;
    ll ans = 0;
    while(i <= n){
        ll j = i + 1;
        while(j <= n && arr[j] - arr[i] <= d){
            j++;
        }
        ll cnt = j - i - 1;
    //  printf("Test (%d,%d) -> %d : %d\n",i,j,cnt,(int)((double)(cnt+1)*((double)cnt/2)));
        ans += (ll)((double)(cnt+1)*((double)cnt/2));
        i = j - 1;
        i++;
    }
    printf("%lld",ans);
    return 0;
}