#include<iostream>
#include<fstream>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
const int NMax=100005;
ifstream fin("lupu.in");
ofstream fout("lupu.out");

int N,X,L;
long long Sol;

vector < pair<int,int> > V;
priority_queue <int> PQ;

void Read()
{
    fin>>N>>X>>L;

    for(int i=1;i<=N;++i)
    {
        int a,b;
        fin>>a>>b;
        a = ( X - a ) / L;
        V.push_back(make_pair(a,b));
    }
}

bool Compare(pair<int,int> A,pair<int,int> B)
{
    return (A.first > B.first);
}

void Solve()
{
    sort(V.begin(),V.end(),Compare);

    int i=0;
    for(int k=V[0].first; k>=0; k--)
    {
        while(V[i].first ==k && i<(int) V.size())
        {
            PQ.push(V[i].second);
            i++;
        }

        if(!PQ.empty())
        {
            Sol += PQ.top();
            PQ.pop();
        }
    }
}

void Print()
{
    fout<<Sol<<"\n";
}

int main()
{
    Read();
    Solve();
    Print();
    return 0;
}