#include <fstream>
#include <algorithm>
#include <vector>
#include <algorithm>
#include <queue>
using namespace std;

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

int N, X, L;
pair <int, int> x;
vector <pair<int,int> > V;

int maximr(-999999999);

priority_queue <int> Q;

int main()
{
    is >> N >> X >> L;
    for ( int i = 1; i <= N; ++i )
    {
        is >> x.first >> x.second;
        x.first = (X-x.first)/L;
        V.push_back(x);
    }

    sort(V.begin(),V.end());
    int it = N-1, Sol = 0;
    for ( int i = 3; i >= 0; --i )
    {


        for ( ; V[it].first == i; --it )
            Q.push(V[it].second);

        if ( !Q.empty() )
            Sol += Q.top(), Q.pop();
    }
    os << Sol;
}