#include <bits/stdc++.h>
using namespace std;

ifstream f("lupu.in");
ofstream g("lupu.out");

const int nmax=100005;
struct oaie {int val,disti,steps;};
oaie a[nmax];
int n,dmax,salt,maxstep=-1;
long long raspuns;

priority_queue <int> cod;

bool cmp (oaie A , oaie B)
{
    return A.steps>B.steps;
}

int main()
{
    int i,k;
    f>>n>>dmax>>salt;
    for (i=1;i<=n;i++)
    {
        f>>a[i].disti>>a[i].val;
        a[i].steps=(dmax-a[i].disti)/salt;
        maxstep=max(maxstep,a[i].steps);
    }

    sort (a+1,a+n+1,cmp);

    i=1;
    for (k=maxstep;k>=0;k--)
    {
       while (a[i].steps==k)
       {
           cod.push(a[i].val);
           i++;
       }

       if (!cod.empty())
       {
           //g<<cod.top()<<'\n';
           raspuns+=cod.top();
           cod.pop();
       }
    }

    g<<raspuns;

    return 0;
}