#include <iostream>
#include <fstream>
#include <utility>
#include <algorithm>
#include <vector>
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");

bool sortbysec(const pair<int,int> &a, 
              const pair<int,int> &b) 
{ 
    return (a.first > b.first); 
} 

int main(){
	int n, x, l, d, lana;
	fin >> n >> x >> l;

	vector<pair<int, int>> v;
	for(int i = 1; i <= n; i++){
		fin >> d >> lana;
		v.push_back(make_pair(d, lana));
	}

   sort(v.begin(), v.end(), sortbysec);
   int copie = v[n].first;
   int pas = 0;
   while(copie <= x){
      pas++;
      copie += l;
   }
   int max = 0;
   int nr = 1;
   int S = 0;
  while(pas){ 
   max = 0;
   for(int i = nr; i <= n; i++){
   	if(v[i].first + l > x){
   	   nr++;
       if(v[i].second > max){
       	max = v[i].second;
       }
   	}else{
   		continue;
   	}
   }
   S += max;
   pas--;
}
fout << S <<" ";
}