#include <fstream>
#include <queue>
#include <algorithm>
#include <queue>

using namespace std;

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

constexpr size_t LIM = 1e5 + 5;

int N, X, L, i, D, A;
pair<int, int> sheep[LIM];
priority_queue<int> pq;
long long ans;

static inline bool compare(
    const pair<int, int>& p1, const pair<int, int>& p2
) {
    return p1.first > p2.first;
}

int main() {
    fin >> N >> X >> L;
    for (i = 1; i <= N; ++i) {
        fin >> D >> A;
        sheep[i] = { D, A }; 
    }

    sort(sheep + 1, sheep + N + 1, compare);

    for (int step = 1, i = 1; i <= N; ++step) {
        int mx = 0;
        for (; sheep[i].first + step * L > X && i <= N; ++i)
            mx = max(mx, sheep[i].second);
        ans += mx;
    }

    fout << ans;

    fin.close();
    fout.close();
    return 0;
}