#include <iostream>
#include <fstream>
#include <queue>
#include <vector>

using namespace std;

ifstream fin("lupu.in");
ofstream fout("lupu.out");
vector<pair<int,int>> v;
priority_queue<int> pq;

int main()
{
    int n,x,l,i,j,a,b,maxi=0,s=0;
    fin>>n>>x>>l;
    for(i=0;i<n;i++)
    {
        fin>>a>>b;
        if(a<=x)
            a=(x-a)/l+1;
        else
            a=0;
        v.push_back(make_pair(a,b));
        maxi=max(maxi,a);
    }
    for(i=maxi;i>=1;i--)
    {
        for(j=0;j<v.size();j++)
        {
            if(v[j].first==i)
                pq.push(v[j].second);
        }
        if(pq.size())
        {
            s+=pq.top();
            pq.pop();
        }
    }
    fout<<s;
    return 0;
}