#include <iostream>
#include <algorithm>
#include <fstream>
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
int n,x,l,d,a,v[100005],idx[100002];
long long s;
struct fa
{
    int dist;
    int lana;
}vi[100002];
bool comp(fa a ,fa b)
{
    if(a.lana>b.lana){
        return 1;
    }
    if(a.lana==b.lana)
    {
        if(a.dist<b.dist)
        {
            return 1;
        }
    }
    return 0;
}
int cmp2(int p, int q)
{
    if(vi[p].dist<vi[q].dist)return 1;
    return 0;
}
int main()
{
    fin>>n>>x>>l;
    for(int i=1;i<=n;i++)
    {
        fin>>d>>a;
        vi[i].lana=a;
        vi[i].dist=d;
    }
    sort(idx+1,idx+1+n,cmp2);
    int k=0,u=0;
    for(int i=1;i<=n;i++)
    {
        vi[i].dist=(x-vi[i].dist)/l;
        if(u<vi[i].dist)
        {
            u=vi[i].dist;
            k++;
            vi[i].dist=k;
        }
        else{
            vi[i].dist=k;
        }
    }
    sort(vi+1,vi+n+1,comp);
    for(int i=1;i<=n;i++)
    {
        if(v[vi[i].dist]==0){v[vi[i].dist]=vi[i].lana;}
        else{
            for(int j=vi[i].dist-1;j>=0;j--)
            {
                if(v[j]==0){v[j]=vi[i].lana;break;}
            }
        }
    }
    int xl1=x/l+1;
    for(int i=0;i<=xl1+1;i++)
    {
        s=s+v[i];
    }
    fout<<s;
    fin.close();
    fout.close();
    return 0;
}