#include<fstream>
#include<algorithm>
#include<queue>

#define NMAX 100005
#define dist v[i].first
#define profit v[i].second
#define PI pair<int,int> 

using namespace std;

int n,x,l;
long long sol;
PI v[NMAX];
priority_queue<int> HEAP;

inline bool cmp(const PI &a,const PI &b)
{
	if(a.first==b.first)
		return a.second>b.second;
	return a.first>b.first;
}

void read()
{
	ifstream fin("lupu.in");
	fin>>n>>x>>l;
	for(int i=0,a;i<n;i++)
	{
		fin>>a>>profit;
		dist=(x-a)/l+1;
	}
	fin.close();
}

void print()
{
	ofstream fout("lupu.out");
	fout<<sol<<'\n';
	fout.close();
}

void solve()
{
	sort(v,v+n,cmp);
	for(int i=0,j=v[0].first;j;j--)
	{
		for(;i<n && j==dist;i++)
			HEAP.push(profit);
		if(!HEAP.empty())
		{
			sol+=HEAP.top();
			HEAP.pop();
		}
	}
}

int main()
{
	read();
	solve();	
	print();
	return 0;
}