#include <iostream>
#include <fstream>
#include <queue>
#include <algorithm>
#define Nmax 100000
using namespace std;
ifstream f("lupu.in");
ofstream g("lupu.out");
long long  n,Dmax,l,sum;
long long lana[Nmax],t[Nmax],Tmax;
bool ins[Nmax];
priority_queue<long long >pq;
int main()
{
    f >> n >> Dmax >> l;
    int x;
    for(int i=1;i<=n;i++){
        f >> x >> lana[i];

        t[i]=(Dmax-x)/l;
        Tmax=max(t[i],Tmax);
    }
    sort(t+1,t+n+1);
    int j=n;
    for(int i=Tmax;i>=0;i--)
    {
        while(t[j]==i && j>0 && !ins[j]){

                ins[j]=1;
                pq.push(lana[j]);
            }
            j--;

            sum+=pq.top();
            pq.pop();
    }

    g << sum;

    return 0;
}