#include <fstream>
#include <cstdlib>
#include <climits>
#include <vector>
#include <algorithm>

#define IN "gutui.in"
#define OUT "gutui.out"

using namespace std;

typedef struct
{
	int h;
	int w;
	int l;
} GUTUIE;

bool cmph ( GUTUIE i, GUTUIE j)
{
	return i.h > j.h;
}

bool cmpw ( GUTUIE i, GUTUIE j)
{
	return i.w < j.w;
}

int main ()
{
	FILE *fin  = fopen (IN, "r");
	FILE *fout = fopen (OUT, "w");
	int i, aux;
	int N, H, U;
	long G = 0;
	fscanf (fin, "%d%d%d", &N, &H, &U);
	vector <GUTUIE> g, Heap;
	make_heap (Heap.begin(), Heap.end(), cmpw);

	for (i = 0; i < N; ++i)
	{
		GUTUIE a;
		fscanf(fin, "%d%d", &a.h, &a.w);
		if (a.h > H)
		{
			aux = 1;
			continue;
		}
		a.l = a.h / U + 1;
		g.push_back(a);
	}

	sort (g.begin(), g.end(), cmph);
/*
	for (i = 0; i < N; ++i)
		fprintf ( fout, "%d %d %d\n", g[i].h, g[i].w, g[i].l );
*/
	if (aux == 1)
	N = (int)g.size();
	int current = g[N-1].l;
	Heap.push_back (g[N-1]);
	push_heap (Heap.begin(), Heap.end(), cmpw);

	for (i = N-2; i >= 0; --i)
	{
		if (g[i].l > g[i+1].l)
		{
			for (; current < g[i].l ; current++)
			{
				if (Heap.size())
				{
					G += Heap.front().w;
					pop_heap (Heap.begin(), Heap.end(), cmpw);
					Heap.pop_back();
				}
			}
		}
		Heap.push_back (g[i]);
		push_heap (Heap.begin(), Heap.end(), cmpw);
	}

	for ( ; current < H/U + 1 && Heap.size() ; ++current)
	{
		G += Heap.front().w;
		pop_heap (Heap.begin(), Heap.end(), cmpw);
		Heap.pop_back();
	}
	fprintf (fout, "%ld\n", G);

	fclose (fin);
	fclose (fout);

	return 0;
}