#include <fstream>
#include <iostream>
#include <set>

using namespace std;

#define x first
#define y second

ifstream f("lupu.in");
ofstream g("lupu.out");

multiset< pair<int,int>, greater<pair<int, int> > > lana;
int n, X, L;
long long s;

void citeste(){

    f >> n >> X >> L;
    for(int i=1; i<=n; i++){
        int d, x;
        f >> d >> x;
        lana.insert(make_pair(x,d));
    }


}

void rezolva(){

    for(int cnt=0; !lana.empty();){
        int val = (*lana.begin()).x;
        int y = (*lana.begin()).y;
        if (y+L*cnt <= X)s+=1LL*val,++cnt;
        lana.erase(lana.begin());
    }

    g << s << "\n";

}

int main(){

    citeste();
    rezolva();

}