#include <bits/stdc++.h>
#define nmax 100005
using namespace std;

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

struct oaie
{
    int t,lana;
    oaie(int t=-1,int lana=0)
    {
        this->t=t;
        this->lana=lana;
    }
    bool operator <(const oaie other)
    {
        return t>other.t;
    }
} oi[nmax];

int main()
{
    int n,x,l;
    in>>n>>x>>l;
    for(int i=0;i<n;i++)
    {
        int d,lana;
        in>>d>>lana;
        oi[i]=oaie((x-d)/l,lana);
    }
    sort(oi,oi+n);
    int64_t res=0;
    priority_queue<int> q;
    int ind=0;
    for(int i=x/l;i>=0;i--)
    {
        while (oi[ind].t==i)
        {
            q.push(oi[ind].lana);
            ind++;   
        }
        if(!q.empty())
        {
            res+=q.top();
            q.pop();
        }
    }
    out<<res;
}