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

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

vector<pair<int, int>> V;

bool cmp(pair<int, int> a, pair<int, int> b) {
    return a.second > b.second;
}

int main() {
    int n, x, l;
    fin >> n >> x >> l;
    int maxim = 0;
    for (int i = 1; i <= n; ++i) {
        int d, a;
        fin >> d >> a;

        if (d <= x) {
            int ind = (x - d) / l + 1;
            V.push_back({ind, a});
            maxim = max(maxim, ind);
        }
    }

    sort(V.begin(), V.end(), greater<pair<int, int>>());

    int vechi = 0;
    long long sum = 0;
    while (vechi < V.size()) {
        int poz = vechi;
        while (V[poz + 1].first == V[vechi].first) {
            poz++;
        }

        sort(V.begin(), V.begin() + poz + 1, cmp);

        sum += V[0].second;
        V.erase(V.begin());

        vechi = poz;
    }

    fout << sum;
    return 0;
}