#include <bits/stdc++.h>

using namespace std;

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

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

oaie v[100];

bool s_f(oaie x, oaie y) {
    return x.blana>y.blana;
}

void marire() {
    for (int i=0;i<n;++i) {
        if (v[i].dist!=-1) {
            v[i].dist+=l;
        }
    }
}
int main() {
    fin>>n>>x>>l;
    for (int i=0;i<n;++i) {
        fin>>v[i].dist>>v[i].blana;
    }

    sort (v, v+n, s_f);

    for (int i=0;i<n;++i) {
        if (v[i].dist<=x) {
            blanaa+=v[i].blana;
            v[i].dist=-1;
            marire();
        }
    }

    fout<<blanaa;
    return 0;
}