#include <bits/stdc++.h>



using namespace std;



ifstream fin  ("lupu.in");

ofstream fout ("lupu.out");



long long n, x, l, i, d, a, m, sol;



pair <long long, long long> v[100005];



multiset <long long> es;



int main(){

    fin >> n >> x >> l;

    for (i=1; i<=n; i++){

        fin >> d >> a;

        if (d <= x){

            v[++m] = {(x-d)/l + 1, a};

        }

    }

    sort (v + 1, v + m + 1);

    for (i=v[m].first; i>=1; i--){

        while (v[m].first == i && m > 0){

            es.insert (-v[m].second);

            m--;

        }

        if (!es.empty()){

            sol += *es.begin();

            es.erase (es.begin());

        }

    }

    fout << -sol;

    return 0;

}