public static boolean isCurrentStCheapest(ArrayList<Station> sList, Station current) {
    int currentValue = current.getCost();

    for (Station s : sList) {
      if (s.getCost() < currentValue) {
        return false;
      }
    }
    return true;
  }
  public static void main(String[] args) {
    Scanner scn = new Scanner(System.in);

    int m = Integer.parseInt(scn.nextLine());

    String s = scn.nextLine();

    String sArr[] = s.split(" ");
    int arr[] = strToIntArr(sArr);

    int n = arr[0];
    int f = arr[1];
    int t = arr[2];
    int l = arr[3];

    Station st[] = new Station[n];

    for (int i = 0; i < n; i++) {
      String ss = scn.nextLine();
      String ssArr[] = ss.split(" ");
      int arr2[] = strToIntArr(ssArr);
      int distance = arr2[0];
      int cost = arr2[1];
      st[i] = new Station(i + 1, cost, distance);
    }

    int cl = 0;
    int sum = 0;

    if (t >= l) {
      System.out.println(sum);
    } else {
      ArrayList<Station> sInit = new ArrayList<Station>();
      int i = 0;
      while (i < n && st[i].getDistance() <= t) {
        sInit.add(st[i]);
        i++;
      }

      sInit.sort(
          new Comparator<Station>() {
            @Override
            public int compare(Station o1, Station o2) {

              return o1.getCost() - o2.getCost();
            }
          });

      if (!sInit.isEmpty()) {
        Station currentSt = (Station) sInit.get(0);

        // System.out.println(currentSt);

        cl = currentSt.getDistance();
        t -= currentSt.getDistance();
        while (cl < l) {
          System.out.println(currentSt);

          int j = currentSt.getIndex();
          ArrayList<Station> sts = new ArrayList<Station>();
          while (j < n && st[j].getDistance() - cl <= f) {
            sts.add(st[j]);
            j++;
          }

          sts.sort(
              new Comparator<Station>() {
                @Override
                public int compare(Station o1, Station o2) {

                  return o1.getCost() - o2.getCost();
                }
              });

          if (isEnd(cl, l, f)) {
            if (isCurrentStCheapest(sts, currentSt)) {
              sum += (l - currentSt.getDistance() - t) * currentSt.getCost();
            } else {
              if (!sts.isEmpty()) {
                int dis = sts.get(0).getDistance() - currentSt.getDistance();
                sum = sum + (dis - t) * currentSt.getCost();
              } else {
                sum += (l - currentSt.getDistance() - t) * currentSt.getCost();
              }
            }
          } else {
            if (isCurrentStCheapest(sts, currentSt)) {
              sum = sum + ((f - t) * currentSt.getCost());
              t = f;
            } else {
              int dis = sts.get(0).getDistance() - currentSt.getDistance();
              sum = sum + (dis - t) * currentSt.getCost();
              t = 0;
            }
          }

          if (!sts.isEmpty()) {
            if (t > 0) {
              t = sts.get(0).getDistance() - currentSt.getDistance();
            }
            currentSt = sts.get(0);
            cl = currentSt.getDistance();

          } else {
            cl = l;
          }
        }
      }

      System.out.println("Final Sum: " + sum);
    }
  }