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

using namespace std;

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

vector < pair <int,int> > O;
int N,X,L;
long long S;
priority_queue <int> Q;

int compare(pair <int ,int > A,pair <int ,int > B)
{
   return A.first<B.first;
}

void Read()
{
    fin>>N>>X>>L;
   for(int i=1;i<=N;i++)
   {
       int a,b;
       fin>>a>>b;
       a=(X-a)/L;
       O.push_back(make_pair(a,b));
   }
   sort(O.begin(),O.end(),compare);
}

void Solve()
{
    int j=N-1;
   for(int i=X/L;i>=0;--i)
   {
       while(O[j].first==i && j>=0)
       {
           Q.push(O[j].second);
           j--;
       }

       if(!Q.empty())
         {
             S=S+Q.top();
             Q.pop();
         }
   }
}

int main()
{
    Read();
    Solve();
    fout<<S;
    return 0;
}