#include <bits/stdc++.h>
using namespace std;
long long int power(long long int a, long long int b) {
  long long int res = 1;
  a %= 1000000007;
  assert(b >= 0);
  for (; b; b >>= 1) {
    if (b & 1) res = res * a % 1000000007;
    a = a * a % 1000000007;
  }
  return res;
}
long long int modInverse(long long int a) { return power(a, 1000000007 - 2); }
const int N = 500023;
bool vis[N];
vector<int> adj[N];
void solve() {
  long long int n, k, l;
  cin >> n >> k >> l;
  vector<long long int> v;
  long long int m = n * k;
  multiset<long long int> s;
  for (long long int i = 0; i < m; i++) {
    long long int c;
    cin >> c;
    v.push_back(c);
    s.insert(c);
  }
  sort((v).begin(), (v).end());
  if ((v[n - 1] - v[0]) > l) {
    cout << 0;
    return;
  }
  long long int ans = 0;
  while (true) {
    if (s.empty()) break;
    for (int i = 1; i < k; i++) {
      auto it = s.end();
      it--;
      s.erase(it);
    }
    auto it = s.lower_bound(v[0] + l + 1);
    it--;
    ans += (*it);
    s.erase(it);
  }
  cout << ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int T = 1;
  int t = 0;
  while (t++ < T) {
    solve();
  }
  cerr << "Time : " << 1000 * ((double)clock()) / (double)CLOCKS_PER_SEC
       << "ms\n";
}
