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

#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;

using ll = long long;

int main() {
    int N, D;
    cin >> N >> D;
    vector<map<int, ll>> mp(3);
    while(N--) {
        int x;
        cin >> x;
        mp[2][x] += mp[1][x - D];
        mp[1][x] += mp[0][x - D];
        mp[0][x] += 1;
    }
    ll ans = 0;
    for(auto [_, v] : mp[2]) ans += v;
    cout << ans << endl;
}