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

struct Oaie
{
    int lana=0, distanta=0;
};

bool cmp(Oaie a, Oaie b) {
    return a.lana > b.lana;
}

std::ifstream in("lupu.in");
std::ofstream out("lupu.out");
Oaie oi[1000001];
int main() {
    int N, X, L;
    in >> N >> X >> L;
    for (int i = 1; i <= N; i++) {
        in >> oi[i].distanta >> oi[i].lana;
    }
    std::sort(oi + 1, oi + N + 1, cmp);
    int pas = 0;
    unsigned long long sol = 0;
    for (int i = 1; i <= N; i++) {
        if (oi[i].distanta + pas * L <= X) {
            sol += oi[i].lana;
            pas++;
        }
    }
    out << sol;
}