#include <bits/stdc++.h>
#define NMAX 100100
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
struct Poz{
    int d, a;
    bool operator<(Poz b)const{
        if(d!=b.d)
            return d<b.d;
        return a<b.a;
    }
} v[NMAX];
int n, x, l, maxi, dist,i;
long long ans;
int main()
{
    fin>>n>>x>>l;
    for( i=1;i<=n;++i)
        fin>>v[i].d>>v[i].a;
    sort(v+1, v+1+n);

//    for(int i=1;i<=n;++i)
//        cout<<v[i].d<<" "<<v[i].a<<'\n';

    i=n;
    dist=l;
    while(i>=1 && dist-l<=x)
    {
        maxi=v[i].a;
        while(i>=1 && v[i].d+dist>x)
        {
            maxi=max(maxi, v[i].a);
            --i;
        }
        ans+=maxi;
      //  cout<<maxi<<" ";
        dist+=l;
    }

    fout<<ans;

    return 0;
}