#include<stdio.h>
#include<algorithm>
using namespace std;
FILE*f=fopen("lupu.in","r");
FILE*g=fopen("lupu.out","w");
int nr,n,x,l;
long long sol;
struct oi
{
	int d,a;
}v[100001];
int cmp(oi a,oi b)
{
	return a.d<b.d;
}
int main()
{
	fscanf(f,"%d%d%d",&n,&x,&l);
	for(int i=1;i<=n;++i)
		fscanf(f,"%d%d",&v[i].d,&v[i].a);
	
	sort(v+1,v+n+1,cmp);
	nr=n;
	long long ll=l;
	while(nr)
	{
		int max=0;
		for(int i=nr;v[i].d+ll>x&&i;--i,--nr)
			if(max<v[i].a)
				max=v[i].a;
			
		sol+=max;
		
		ll+=l;
	}
	fprintf(g,"%lld",sol);
	
	fclose(f);
	fclose(g);
	return 0;
}