#include <fstream>
#include <algorithm>
#include <queue>

using namespace std;

ifstream cin ("lupu.in");
ofstream cout ("lupu.out");

const int nmax = 100000;

struct Oaie {
  int dist;
  int val;
}v[1 + nmax];

int n, x, l;
long long sol;

priority_queue <int> pq;

bool comp(Oaie a, Oaie b) {
  if(a.dist == b.dist)
    return a.val < b.val;
  return a.dist < b.dist;
}

int main() {
  cin >> n >> x >> l;
  for(int i = 1; i <= n; i++) {
    cin >> v[i].dist >> v[i].val;
    v[i].dist = (x - v[i].dist) / l;
  }
  sort(v + 1, v + n + 1, comp);
  int j = n;
  for(int i = v[n].dist; i >= 0; i--) {
    while(v[j].dist == i && j >= 1) {
      pq.push(v[j].val);
      j--;
    }
    if(!pq.empty()) {
      sol += pq.top();
      pq.pop();
    }
  }
  cout << sol;
  return 0;
}