#include <iostream>
#include <algorithm>
#include <stack>
#include <queue>
#include <fstream>

using namespace std;

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

const int NMax = 100000 + 5;

int N,X,L,runDist,sol;

struct elem {
    int dist,val;
}v[NMax];

bool cmp (elem a,elem b) {
    return a.val>b.val;
}

int main() {
    in>>N>>X>>L;

    for (int i=1;i<=N;++i) {
        in>>v[i].dist>>v[i].val;
    }

    sort(v+1,v+N+1,cmp);

    sol = runDist = 0;
    for (int i=1;i<=N;++i) {
        if (v[i].dist + runDist <= X) {
            sol += v[i].val;
            runDist += L;
        }
    }

    out<<sol;
    return 0;
}