#include <fstream>
#include <algorithm>

using namespace std;

ifstream fin ("lupu.in");
ofstream fout ("lupu.out");

int urm = 1, n, x, l, v[100001], d, k, y;
long long total;

struct oaie  {
  int nr, val;
} o[100001];

bool cmp (oaie a, oaie b)  {
  return (a.val > b.val || a.val == b.val && a.nr < b.nr);
}

int main()  {
  fin >> n >> x >> l;
  for (int i = 1; i <= n; ++i)  {
    fin >> d >> o[i].val;
    o[i].nr = (x - d) / l + 1;
    if (o[i].nr > k)
      k = o[i].nr;
  }
  sort (o + 1, o + n + 1, cmp);
  for (int i = 1; i <= k; ++i)  {
    y = o[i].nr;
    while (v[y])
      --y;
    if (y != 0)
      v[y] = true, total += o[i].val;
    else if (k < n)
      ++k;
  }
  fout << total;
}