#include <fstream>
#include <algorithm>
#include <set>

#define f first
#define s second

using namespace std;

multiset <int> v;
multiset <int>::iterator it;
pair <int,int> a[100005];

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

long long sum;
int n,x,l,maxim,i,d;

int main()
{
    fin >> n >> x >> l;
    for (i=1;i<=n;i++)
    {
        fin >> a[i].f >> a[i].s;
        a[i].f=(x-a[i].f)/l;
        if (a[i].f>maxim) maxim=a[i].f;
    }
    sort (a+1,a+n+1);
    i=n;
    for (d=maxim;d>=0;d--)
    {
        while (a[i].f==d && i>=1)
        {
            v.insert(a[i].s);
            i--;
        }
        if (!v.empty())
        {
            it=v.end();
            it--;
            sum+=*it;
            v.erase(it);
        }
    }
    fout << sum;

    return 0;
}