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

using namespace std;
struct lup
{
	long long int a, b;
}v[100005];
int cmp(lup x, lup y)
{
	return x.a<y.a;
}
priority_queue<int> f;
int main()
{
	ifstream cin("lupu.in");
	ofstream cout("lupu.out");
	long long int n, x, l, s=0, h=0;
	cin>>n>>x>>l;
	for(int i=0; i<n; i++)
    {
        cin>>v[i].a>>v[i].b;
    }
	sort(v,v+n,cmp);
    for(int i=0; i<=x; i+=l)
	{
		while(h<n && v[h].a<=i)
		{
			f.push(v[h].b);
			h++;
		}
		if(f.size()!=0)
		{
			s+=f.top();
			f.pop();
		}
	}
	cout<<s;
    return 0;
}