#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
vector < pair < long long, long long > > V;
int N, L, D;
void Read()
{
    fin >> N >> L >> D;
    for(int i = 1; i <= N; ++ i)
    {
        int A, B;
        fin >> A >> B;
        V.push_back(make_pair(B, A));
    }
    sort(V.begin(), V.end(), greater < pair < int, int > >());
}
void Task()
{
    int R = D;
    long long SUM = 0;
    vector < pair < int, int > > :: iterator it = V.begin();
    SUM += it -> first;
    advance(it, 1);
    while(it != V.end())
    {
        if(it -> second + D <= L)
        {
            D += R;
            SUM += it -> first;
        }
        advance(it, 1);
    }
    fout << SUM;
}
int main()
{
    Read();
    Task();
    return 0;
}