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

ifstream fin("lupu.in");
ofstream fout("lupu.out");

priority_queue <pair <long long, long long>> p;

int main()
{
    long long nr, n, x, l, i;
    pair <long long, long long> o;
    nr = 0;
    fin >> n >> x >> l;
    for (i = 1; i<=n; i++)
    {
        fin >> o.second >> o.first;
        p.push(o);
    }
    long long rasp = 0;
    while (p.empty() == 0)
    {
        if (p.top().second + nr*l <= x)
        {
            rasp = rasp + p.top().first;
            nr++;
        }
        p.pop();
    }
    fout << rasp;
    return 0;
}