#include <iostream>
#include <fstream>
#include <cmath>
#include <algorithm>

using namespace std;

ifstream f("lupu.in");
ofstream g("lupu.out");

int maxi(pair<int,int>v[100000],int b){
int i;
int rez;//indicele elem maxim din v
int maxim=0;
for(i=0;i<=b;i++)
    if(v[i].second>maxim)
    {
        rez=i;
        maxim=v[i].second;
    }
return rez;
}

int cmp(const pair<int,int>&p,const pair<int,int>&q)
{
    if(p.first==q.first)
        return(p.second<q.second);
    return p.first<q.first;
}

int main()
{
    int n,x,l,i;
    pair<int,int>v[100000];
    f>>n>>x>>l;
    for(i=0;i<n;i++)
        f>>v[i].first>>v[i].second;

     sort(v,v+n,cmp);//sortez in functie de distanta-crescator

  int r;
  int k,s=0;
int nr_intervale=x/l;
if(x%l!=0)
    nr_intervale++;

for(k=1;k<=nr_intervale;i++)
    while(n!=0)
{
        r=maxi(v,n-l+1);

        s+=v[r].second;//cantitatea de lana stransa
         v[r].second=-1;
//cout<<s<<endl;
//cout<<r.first<<" "<<r.second<<endl;
        n=n-l;
}
cout<<s;
    return 0;
}