#include<bits/stdc++.h>
#define mp make_pair
#define PII pair<int,int>
#define fi first
#define se second
using namespace std;

ifstream fin("lupu.in");
ofstream fout("lupu.out");

const int NMAX=100005;

int n,x,l;
PII a[NMAX];
long long sol;

inline bool cmp(const PII A,const PII B)
{
    if (A.fi==B.fi) return A.se<B.se;
    return A.fi<B.fi;
}

int main()
{
    int i,aux,mx,cnt=0;
    bool ok=0;
    fin>>n>>x>>l;
    for (i=1;i<=n;i++) fin>>a[i].se>>a[i].fi;
    sort(a+1,a+n+1,cmp);
    for (i=n;i>=1;i--)
        {
            if (x<a[i].se) aux=0;
            else aux=((x-a[i].se)/l)+1;
            if (aux>0)
                {
                    if (ok==0) {mx=aux;ok=cnt=1;sol+=a[i].fi;}
                    else if (aux>mx || cnt<mx)
                            {
                                sol+=a[i].fi;
                                mx=max(mx,aux);
                                cnt++;
                            }
                }
        }
    fout<<sol<<"\n";
    return 0;
}