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

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

priority_queue<pair<int, int>> PQ;

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

        PQ.push({a, d});
    }

    int timp = 0;
    int sum = 0;
    while (PQ.size() && timp <= x) {
        while (PQ.size() && PQ.top().second + timp > x) {
            PQ.pop();
        }
        if (PQ.size()) {
            sum += PQ.top().first;
            PQ.pop();
        }
        timp += l;
    }

    fout << sum;
    return 0;
}