#include <bits/stdc++.h>

using namespace std;

FILE *fin = fopen ("lupu.in", "r"), *fout = fopen ("lupu.out", "w");

const int MAXN = 1e5;

pair <int, int> a[MAXN + 1];

priority_queue <int> heap;

int main() {
  int n, x, l, i, j, d;
  long long sol;
  fscanf (fin, "%d%d%d", &n, &x, &l);
  for (i = 1; i <= n; i++) {
    fscanf (fin, "%d%d", &a[i].first, &a[i].second);
  }
  sort (a + 1, a + n + 1);
  j = 1;
  sol = 0;
  for (d = 0; d <= x; d = d + l) {
    while (j <= n && a[j].first <= d) {
      heap.push (a[j++].second);
    }
    if (heap.empty () == false) {
      sol = sol + heap.top ();
      heap.pop ();
    }
  }
  fprintf (fout, "%lld\n", sol);
  fclose (fin);
  fclose (fout);
  return 0;
}