#include <bits/stdc++.h>
using namespace std;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N,D; cin >> N >> D;
    map<long long,long long> M1,M2;

    long long answer = 0;
    while(N--){
        int a; cin >> a;
        M1[a]++;
        if(M1.count(a-D)) M2[a] += M1[a-D];
        if(M2.count(a-D)) answer += M2[a-D];
    }

    cout << answer << endl;
}