#include <iostream>
#include <stdio.h>
#include <algorithm>
#include <fstream>
using namespace std;
ifstream f("lupu.in");
ofstream g("lupu.out");

#define NMAX 100001

int n, X, L;

struct Oaie{
    int dist, lana;
};

Oaie v[NMAX];

int compare(Oaie x, Oaie y) {
    return x.lana > y.lana;
}

int main()
{
    freopen("lupu.in", "r", stdin);
    freopen("lupu.out", "w", stdout);

    int i, D;
    long long cost = 0;

    scanf("%d %d %d", &n, &X, &L);

    for(i = 1; i <= n; i++)
        scanf("%d %d", &v[i].dist, &v[i].lana);

    sort(v + 1, v + n + 1, compare);

    D = 0;
    for(i = 1; i <= n; i++) {
        if(v[i].dist + D <= X) {
            cost += v[i].lana;
            D += L;
        } else continue;
    }

    g<<cost<<'\n';

    return 0;
}