#include <iostream>
#include <fstream>
#include <queue>
using namespace std;
ifstream f("lupu.in");
ofstream g("lupu.out");
priority_queue<unsigned long long int> coada;
int n,ok;
unsigned long long int x,l,suma;
struct
{
    unsigned long long int d,val;
}v[20001],aux;
int partitie (int l,int r)
{
    int pivot=v[r].d,poz=l-1;
    for(int j=l;j<=r;j++)
    {
        if(v[j].d<=pivot)
        {
            poz++;
            aux=v[poz];
            v[poz]=v[j];
            v[j]=aux;
        }
    }
    return poz;
}
void quicksort(int l,int r)
{
    if(l<r)
    {
     int pivot=partitie(l,r);
     quicksort(l,pivot-1);
     quicksort(pivot+1,r);
    }
}
int main()
{
   f>>n>>x>>l;
   for(int i=1;i<=n;i++)
    f>>v[i].d>>v[i].val;
   quicksort(1,n);
    for(int i=1;i<=n;i++)
    {
        ok=1;
        int calc=(x-v[i].d)/l;
        coada.push(v[i].val);
        while(ok)
        {
         int calc2=(x-v[++i].d)/l;
         if(calc2==calc)
            coada.push(v[i].val);
            else
            ok=0;
        }
        --i;
        suma+=coada.top();
        coada.pop();
    }
    g<<suma;
    return 0;
}