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

using namespace std;

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

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

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

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().dist<<" "<<pq.top().blana<<endl;
    //     pq.pop();
    // }
    int ll=0 ;
    while (pq.size()>0) {
        int  b_m_loc=-1;
        while (pq.size()>0 && pq.top().dist+ll+l>x) {
            b_m_loc=max(b_m_loc,pq.top().blana);
            // if (pq.size()==1) {
            //     break;
            // }
            pq.pop();

        }
        blanaa+=b_m_loc;
        // if () {
        //     blanaa+=pq.top().blana;
        //     //cout<<pq.top().blana<<" "<<pq.top().dist+ll<<endl;
        ll+=l;
        //
        // }

    }

    fout<<blanaa;
    return 0;
}