#include <bits/stdc++.h>

using namespace std;

ifstream fin ( "lupu.in" ) ;
ofstream fout ( "lupu.out" ) ;
pair<int,int> v[100005];
signed main()
{

    int n , x , l ;
    fin >> n >> x >> l ;
    for ( int i = 1 ; i <= n ; ++ i )
        fin >> v[i].first >> v[i].second;
    sort(v+1,v+n+1);
    int suma = 0;
    for ( int r = 0 ; r * l <= x ; ++ r )
    {
        int j = 1 ;
        priority_queue<int>pq;
        while ( j <= n && v[j].first + r * l <= x ){
            if ( v[j].first + (r+1)*l > x )
                pq.push(v[j].second);
            ++j;
            }
        if ( !pq.empty() )
        {
            suma += pq.top() ;
            pq.pop();
        }
    }
    fout << suma ;
    return 0;
}