#include <bits/stdc++.h>
#define int long long

using namespace std;

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

int n, x, l, blanaa=0;
struct oaie {
    int dist, blana;

    bool operator<(const oaie &o) const {
        if (blana != o.blana) {
            return blana < o.blana;
        }
        else {
            return dist > o.dist;
        }
    }
};

oaie v[100000];
priority_queue<oaie> pq;





signed main() {
    fin>>n>>x>>l;
    for (int i=0;i<n;++i) {
        fin>>v[i].dist>>v[i].blana;
        pq.push(v[i]);
        //cout<< pq.top().blana<<endl;
    }

    // for (int i=0;i<n;++i) {
    //     cout<<pq.top().blana<<" ";
    //     pq.pop();
    // }
    int ll=0;
    for (int i=0;i<n;++i) {
        if (pq.top().dist+ll<=x) {
            blanaa+=pq.top().blana;
            //cout<<pq.top().blana<<" "<<pq.top().dist+ll<<endl;
            ll+=l;

        }
        pq.pop();
    }

    fout<<blanaa;
    return 0;
}