task966

#define loop(i,from,to) for (int i = from; i < to; ++i)
#define qAll(q) q.begin(), q.end()
#include <bits/stdc++.h>

using std::cin;
using std::cout;
using std::endl;
using std::vector;
using std::string;
using std::pair;
using std::set;

const int INF = 1e9+7;
const double eps = 1e-6;
template <typename T> void reverse(T &a) {
  long long s = a.size();
  for (long long i = 0; i < s / 2; ++i)
    std::swap(a[i], a[s - i - 1]);
}


signed main() {
  std::ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie();

  int n, l, r, v, t; cin >> n;
  vector< vector<int> > data(n);
  loop(i, 0, n) {
    cin >> l >> r >> v;
    data[i].emplace_back(l);
    data[i].emplace_back(r);
    data[i].emplace_back(v);
  }
  cin >> t;
  vector<int> timeline(t, 0);

  std::sort(data.begin(), data.end());
  loop(i, 0, n)
    loop(j, data[i][0], t - 1) {
      if (j > data[i][1]) break;
      timeline[j] += data[i][2];
    }
  cout << timeline[t - 1];
  //std::cout << "Hello World!\n";
  return 0;
}