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

#define isin(l, x, r) (l <= x && x < r)
#define rep(i, n) for (int i = 0; (i) < (int)(n); ++(i))
#define rep3(i, m, n) for (int i = (m); (i) < (int)(n); ++(i))
#define rep_r(i, n) for (int i = (int)(n) - 1; (i) >= 0; --(i))
#define rep3r(i, m, n) for (int i = (int)(n) - 1; (i) >= (int)(m); --(i))
#define all(x) begin(x), end(x)
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())

using ll = long long;
using PI = std::pair<int, int>;
using PLL = std::pair<ll, ll>;
using VI = std::vector<int>;
using VLL = std::vector<ll>;

template <typename T>
using PQ = std::priority_queue<T, std::vector<T>, std::greater<T>>;

template <typename T>
bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b; // aをbで更新
    return true;
  }
  return false;
}

template <typename T>
bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b; // aをbで更新
    return true;
  }
  return false;
}

/*
#define rad_to_deg(rad) (((rad)/2/M_PI)*360)
cout << std::fixed << std::setprecision(15) << y << endl;
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};
*/

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

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

#ifdef LOCAL
#include <debug.h>
#else
#define dlog(...)
#endif

ll solve(int N, ll K, const std::vector<ll> &A) {
  auto mx = *max_element(all(A));
  VLL a(mx * 2 + 10);
  rep(i, N) a[A[i]]++;
  if (K > mx * 2) return 0;
  auto c = convolution_ll(a, a);
  return c[K];
}

// generated by oj-template v4.8.1 (https://github.com/online-judge-tools/template-generator)
int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  cout << std::fixed << std::setprecision(15);
  int n;
  ll k;
  std::cin >> n;
  std::vector<ll> a(n);
  std::cin >> k;
  rep(i, n) {
    std::cin >> a[i];
  }
  auto ans = solve(n, k, a);
  std::cout << ans << '\n';
  return 0;
}