#include <fstream>
#include <queue>

using namespace std;

ifstream cin("lupu.in");
ofstream cout("lupu.out");

struct pr
{
    int val, timp;
};

pr v[100005];
int n, x, l;

bool b(pr a, pr b)
{
    //if(a.val == b.val)
    //    return a.timp < b.timp;
    return a.val < b.val;
}

void citire()
{
    cin >> n >> x >> l;

    for(int i = 0 ; i < n ; i++)
        cin >> v[i].timp >> v[i].val;
}

void rez()
{
    priority_queue< pr, vector<pr>, bool(*)(pr, pr) > q(b);

    for(int i = 0 ; i < n; i++)
        q.push(v[i]);

    long long d = 0, sum = 0;

    /*while(!q.empty())
    {
        cout << q.top().timp << ' ' << q.top().val << '\n';
        q.pop();
    }*/

    while(!q.empty() && d <= x)
    {
        while(q.top().timp + d > x)
            q.pop();
        sum += q.top().val;

        /*cout << q.top().timp << ' ' << d <<
        ' ' << q.top().val <<' ' << sum << '\n';*/
        d += l;
        q.pop();
    }

    cout << sum;
}

int main()
{
    citire();
    rez();
    return 0;
}