#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>

using namespace std;

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

#define nmax 100100
#define f first
#define s second
#define mp make_pair

pair <int,int> v[nmax];
int k,n,i,x,a,b,l;
long long ans;

bool compare(const pair<int,int> &a, const pair<int,int> &b)
{
    return a.f>b.f;
}


int main()
{
    fin>>n>>x>>l;
    for(i=1; i<=n; ++i)
    {
        fin>>a>>b;
        v[i]=mp(b,a);
    }
    sort(v+1,v+n+1,compare);
    k=0;
    for(i=1; i<=n; ++i)
    {
        if(v[i].s+k*l<=x)
        {
            ++k;
            ans+=v[i].f;
        }
    }
    fout<<ans;
}