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

struct Sheep {
private:
    size_t wool = 0;
public:
    size_t distance = 0, max_step = 0;

    size_t getWool() const {
        return wool;
    }

    Sheep() = default;

    explicit Sheep(std::istream &istream) {
        istream >> distance >> wool;
    }

    static bool cmp_by_step(const Sheep &_lhs, const Sheep &_rhs) {
        return _lhs.max_step < _rhs.max_step;
    }
};

inline bool operator<(const Sheep &_lhs, const Sheep &_rhs) {
    return _lhs.getWool() < _rhs.getWool();
}

int main() {
    std::ifstream input("lupu.in");
    std::ofstream output("lupu.out");

    std::priority_queue<Sheep, std::vector<Sheep>> woolQueue;
    size_t n, wolf_max_distance, increment;
    std::vector<Sheep> sheep;
    input >> n >> wolf_max_distance >> increment;
    sheep.reserve(n);
    for (size_t i = 0; i < n; ++i) {
        Sheep a(input);
        a.max_step = (wolf_max_distance - a.distance) / increment + 1;
        sheep.push_back(a);
    }
    size_t max_step = std::max_element(sheep.cbegin(), sheep.cend(), Sheep::cmp_by_step)->max_step, total_wool = 0;
    for (size_t i = max_step; i >= 1; --i) {
        for (int j = 0; j < n; ++j) if (sheep[j].max_step == i) woolQueue.push(sheep[j]);
        
        if (!woolQueue.empty()) {
            total_wool += woolQueue.top().getWool();
            woolQueue.pop();
        }
    }
    output << total_wool;
    return 0;
}