//
//  main.cpp
//  lupu
//
//  Created by Alex Petrache on 19/01/15.
//  Copyright (c) 2015 Alex Petrache. All rights reserved.
//

#include<fstream>
#include<algorithm>
#include<queue>

using namespace std;

int n,x,l,i,d;
priority_queue<int>q;

struct oaie
{
    int t,l;
}v[100009];

bool cmp(oaie a,oaie b)
{
    return (a.t>b.t);
}

int main()
{
    ifstream f("lupu.in");
    ofstream g("lupu.out");
    f>>n>>x>>l;
    for (i=1;i<=n;++i)
    {
        f>>d>>v[i].l;
        if (d<=x)
            v[i].t=(x-d)/l+1;
    }
    
    sort(v+1,v+n+1,cmp);
    
    i=1;
    long long sum=0,k;
    for (k=v[i].t;k>0;k--)
    {
        while (i<=n && v[i].t==k)
        {
            q.push(v[i].l);
            i++;
        }
        if (!q.empty()) {sum+=q.top();q.pop();}
    }
    g<<sum<<'\n';
    return 0;
}