/*
    VASILESCU Laura-Mihaela, grupa 325CA
    tema 1 * PA
*/

#include <stdio.h>
#include <stdlib.h>

typedef struct heap
{
	void **elem;
	int dimensiune/*dimensiune heap*/,capacitate/*capacitatea maxima a vectorului*/;
} Heap;

Heap createHeap ()
{
	Heap H;
	H.elem = (void**)calloc(1, sizeof(void*));
	H.capacitate = 1;
	H.dimensiune = 0;
	return H;
}

int dimHeap (Heap H)
{
	return H.dimensiune;
}

int capacitHeap (Heap H)
{
	return H.capacitate;
}

int parinte (Heap H, int poz)
{
	int p;
	p = (poz - 1)/2;
	if (p < 0)
		return -1;
	return p;
}

int stHeap (Heap H, int poz)
{
	int p;
	p = 2*poz + 1;
	if (p >= dimHeap(H))
		return -1;
	return p;
}

int drHeap (Heap H, int poz)
{
	int p;
	p = 2*poz + 2;
	if (p >= dimHeap(H))
		return -1;
	return p;
}

void * elem_atHeap (Heap H, int poz)
{
	if (poz < 0 || poz >= dimHeap(H))
		return NULL;
	return H.elem[poz];
}

void exchangeHeap (Heap *H, int p1, int p2)
{
	if (p1 < 0 || p1 >= dimHeap(*H))
		return;
	if (p2 < 0 || p2 >= dimHeap(*H))
		return;
	void *aux;
	aux = elem_atHeap(*H, p1);
	H->elem[p1] = elem_atHeap(*H, p2);
	H->elem[p2] = aux;
}

void urcareHeap (Heap *H, int p, int (*f)())
{
	while (parinte(*H,p) >= 0 && f(elem_atHeap(*H, p), elem_atHeap(*H, parinte(*H, p))) < 0)
	{
		exchangeHeap(H,p,parinte(*H,p));
		p = parinte(*H, p);
	}
}

void * min_nodHeap (Heap H, int poz, int (*f)())
{
	void *min = elem_atHeap(H,poz);
	if (elem_atHeap(H, stHeap(H, poz)) != NULL)
		if (f(min, elem_atHeap(H, stHeap(H, poz))) > 0)
			min = elem_atHeap(H, stHeap(H, poz));
	if (elem_atHeap(H, drHeap(H, poz)) != NULL)
		if (f(min, elem_atHeap(H, drHeap(H, poz))) > 0)
			min = elem_atHeap(H, drHeap(H, poz));
	return min;
}

void coboaraHeap (Heap *H, int p, int (*f)())
{
	while (1)
	{
		void *min = min_nodHeap(*H, p, f);
		if (min == elem_atHeap(*H, p))
			break;
		int pe = 0;
		if (min == elem_atHeap(*H, stHeap(*H, p)))
			pe = stHeap(*H, p);
		if (min == elem_atHeap(*H, drHeap(*H, p)))
			pe = drHeap(*H, p);
		exchangeHeap(H, p, pe);
		p = pe;
	}
}

void insertHeap (Heap *H, void *x, int (*f)())
{
	H->dimensiune++;
	if (H->dimensiune == H->capacitate)
	{
		H->elem = (void**)realloc(H->elem, (2*(H->capacitate) + 1)*sizeof(void*));
		H->capacitate = 2*(H->capacitate) + 1;
	}
	H->elem[dimHeap(*H)-1] = x;
	int p = dimHeap(*H) - 1;
	urcareHeap(H, p, f);
}

void * extrageHeap (Heap *H, int (*f)())
{
	if (dimHeap(*H) < 1)
		return NULL;
	void *x;
	x = elem_atHeap(*H,0);
	exchangeHeap(H, 0, dimHeap(*H) - 1);
	H->dimensiune--;
	coboaraHeap(H, 0, f);
	return x;
}


typedef struct obiecte {
    long inaltime;
    long greutate;
    long round;
} Obiecte;

int comparator (const void *O1, const void *O2)
{
    Obiecte *o1, *o2;
    o1 = (Obiecte *)O1;
    o2 = (Obiecte *)O2;
    if (o1->round < o2->round)
        return -1;

    if (o1->round == o2->round) {
        if (o1->greutate < o2->greutate)
            return 1;
        else
            if (o1->greutate == o2->greutate)
                return 0;
            else
                return -1;
    }

    return 1;
}

int compHeap (void *a, void *b)
{
    Obiecte *o1, *o2;
    o1 = (Obiecte *)a;
    o2 = (Obiecte *)b;
    if (o1->greutate < o2->greutate)
        return -1;
    else
        if (o1->greutate == o2->greutate)
            return 0;
    return 1;
}

int main()
{
    FILE *f = fopen("gutui.in", "r");
    FILE *g = fopen("gutui.out", "w");

    long N, H, U, G = 0, i, *obj;
    Obiecte *gutui;

    /* Numărul de gutui */
    fscanf(f, "%ld", &N);
    gutui = calloc(N, sizeof(Obiecte));
    obj = calloc(N + 1, sizeof(long));

    /* Înălțimea maximă la care poate ajunge Gigel */
    fscanf(f, "%ld", &H);

    /* Cu cât se ridică crengile */
    fscanf(f, "%ld", &U);

    for (i = 0; i < N; i++) {
        fscanf(f, "%ld", &gutui[i].inaltime);
        fscanf(f, "%ld", &gutui[i].greutate);
        gutui[i].round = (H - gutui[i].inaltime) / U + 1;
    }

    qsort(gutui, N, sizeof(Obiecte), comparator);

    long k = 0;

    Heap heap = createHeap();
    
    /* Elimin gutuile la care nu pot ajunge */
    for (i = 0; i < N; i++){ 
        if (k < gutui[i].round) {
            k++;
            G += gutui[i].greutate;
            insertHeap(&heap, &gutui[i], compHeap);
            break;
        }
    }

    for (i++; i < N; i++) {
        if (k < gutui[i].round) {
            k++;
            G += gutui[i].greutate;
            insertHeap(&heap, &gutui[i], compHeap);
        }
        else {
            /* caut în heap un element cu greutate mai mică */
            Obiecte *gutuie;
            gutuie = (Obiecte *)elem_atHeap(heap, 0); /* greutatea minimă din heap */
            if (gutuie->greutate < gutui[i].greutate) {
                G -= gutuie->greutate;
                G += gutui[i].greutate;
                gutuie = extrageHeap (&heap, compHeap);
                insertHeap(&heap, &gutui[i], compHeap);
            }
        }
    }

    fprintf(g, "%ld", G);

    return 0;
}