#include<fstream>
#include<queue>
#include<algorithm>
using namespace std;
ifstream f("lupu.in");
ofstream g("lupu.out");
struct oaie {
    int dist;
    int puf;
    int t;
} a[100002];
bool cmp(oaie x, oaie y)
{
    if(x.t==y.t)
        return x.puf>=y.puf;
    return x.t>=y.t;
}
priority_queue <int, vector<int> > heap;
int n, d, l, k, s, i, ii, t[100002], tmax;
int main ()
{
    f>>n>>d>>l;
    for(i=1;i<=n;i++)
    {
        f>>a[i].dist>>a[i].puf;
        if(a[i].dist>d)
        {
            a[i].t=2147483648;
            continue;
        }
        if(l!=0)
        {
            a[i].t=(d-a[i].dist)/l+1;
            if(a[i].t>tmax)
            {
                tmax=a[i].t;
                continue;
            }
        }
        else
        {
            a[i].t=d-a[i].dist+1;
            if(a[i].t>tmax)
            {
                tmax=a[i].t;
                continue;
            }
        }
        if(a[i].t<0)
            a[i].t=2147483648;
    }
    sort(a+1, a+n+1, cmp);
    ii=1;
    while(a[ii].t!=tmax)
        ii++;
    for(i=tmax;i>0;i--)
    {
        int j=ii;
        for(;j<=n;j++)
            if(a[j].t==i)
                heap.push(a[j].puf);
        s+=heap.top();
        heap.pop();
    }
    /*for(i=1;i<=n;i++)
        g<<a[i].t<<" ";*/
    g<<s;
    return 0;
}