#include<fstream>
#include<queue>
#include<algorithm>
using namespace std;
ifstream f("lupu.in");
ofstream g("lupu.out");
struct oaie {
    int dist;
    int puf;
} a[90];
bool cmp(oaie a, oaie b)
{
    if(a.puf==b.puf)
        return a.dist>=b.dist;
    return a.puf>=b.puf;
}
priority_queue <int, vector<int> > heap;
int n, d, l, k, s, i;
int main ()
{
    f>>n>>d>>l;
    for(i=1;i<=n;i++)
        f>>a[i].dist>>a[i].puf;
    sort(a+1,a+n+1, cmp);
    i=1;
    while(i<=n)
    {
        int ii=i;
        while(a[ii].dist+k<=d)
        {
            heap.push(a[ii].puf);
            k+=l;
            ii++;
        }
        i++;
    }
    while(!heap.empty())
    {
        s+=heap.top();
        heap.pop();
    }
    g<<s;
    return 0;
}