#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin ("lupu.in");
ofstream fout ("lupu.out");
struct oaie
{
    long D,A;
} oi[100001];
long n,x,l,lana;
long k;
bool comp (oaie o1, oaie o2)
{
    return o1.D<o2.D;
}
int alegeoaie()
{
    for(long i=1; i<=n; i++)
    {
        if(oi[i].D<=x && oi[i].A!=-1)
        {
            return i;
        }
    }
    return 0;
}
int main()
{
    fin>>n>>x>>l;
    for(long i=1; i<=n; i++)
        fin>>oi[i].D>>oi[i].A;
    sort(oi+1,oi+n+1,comp);

    while(alegeoaie())
    {
        k=alegeoaie();
        for(long j=1; j<=n; j++) oi[j].D+=l;
        lana+=oi[k].A;
        oi[k].A=-1;
    }
    fout<<lana;
    return 0;
}