#include <fstream>
#include <algorithm>
#include<queue>
using namespace std;
ifstream cin("lupu.in");
ofstream cout ("lupu.out");
int n,x,l,d,nrh;
long long s;
priority_queue <int> h;
struct oi
{
    int c,s;
};
oi v[100005];

int cmp (oi a, oi b)
{
    if(a.s>b.s)
        return 1;
    return 0;
}

int main ()
{
    cin>>n>>x>>l;
    for(int i=1;i<=n;i++)
    {
        cin>>d>>v[i].c;
        v[i].s=(x-d)/l+1;

    }
    sort(v+1,v+n+1,cmp);
    /*
    for(int i=1;i<=n;i++)
        cout<<v[i].c<<" "<<v[i].s<<"\n";
    */
    int j=1;
    for(int i=x/l+1;i>=1;i--)
    {
        while(j<=n && v[j].s==i)
        {
           h.push(v[j].c);
            j++;
        }
        if(!h.empty())
        {
           s+=h.top();
           h.pop();
        }
    }
    cout<<s;
    return 0;
}