#include<queue>
#include<fstream>
using namespace std;
ifstream in("lupu.in");
ofstream out("lupu.out");
const int N=100010;

int n,q,r;

priority_queue<pair<int,int> > c;

void read()
{
	in>>n>>r>>q;
	int d,a;
	for(int i=1;i<=n;i++)
	{
		in>>d>>a;
		c.push(make_pair(a,d));
	}
}

void solve()
{
	long long s = 0, dist = 0;
	pair<int,int> x;
	while(!c.empty())
	{
		while(!c.empty())
		{
			x = c.top();
			c.pop();
			if(x.second + dist <= r)
			{
				s += x.first;
				dist += q;
				break;
			}
		}
	}
	out<<s<<"\n";
}

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