#include <bits/stdc++.h>

using namespace std;

struct Oaie {
public:
    int lana, poz;
};

vector<Oaie> oi;
priority_queue<int> oiPrinse;

int compare(Oaie a, Oaie b) {
    return a.poz < b.poz;
}

int main()
{
    int N, X, L;
    freopen("lupu.in", "r", stdin);
    freopen("lupu.out", "w", stdout);

    cin>>N>>X>>L;
    oi.resize(N);
    for (int i = 0; i < N; ++i) {
        cin>>oi[i].poz>>oi[i].lana;
    }

    sort(oi.begin(), oi.end(), compare);

    int nrIncercari = X % L, i = 0, sm = 0;
    while(nrIncercari <= X) {
        for(; i < N && oi[i].poz <= nrIncercari; ++i)
            oiPrinse.push(oi[i].lana);

        if (!oiPrinse.empty()) {
            sm += oiPrinse.top();
            oiPrinse.pop();
        }

        nrIncercari += L;
    }

    cout<<sm;
}