#include <stdio.h>
#include <vector>
#include <algorithm>
#define N 100000

using namespace std;

typedef struct {
	unsigned long w, h, pos;
} quince;

unsigned long n, hmax, u;
vector<quince> v, heap;

void read() {
	unsigned int i;

	scanf("%lu %lu %lu", &n, &hmax, &u);

	for ( i = 0; i < n; i++ ) {
		quince e;
		scanf("%lu %lu", &e.h, &e.w);
		e.pos = (hmax - e.h)/u + 1;

		v.insert(v.end(), e);
	}
}

void print() {
	unsigned int i;
	
	for ( i = 0; i < v.size(); i++ )
		printf("%lu %lu %lu\n", v[i].h, v[i].w, v[i].pos);
}

bool quinceCmpWeight (const quince q1, const quince q2) {
	if (q1.w < q2.w)
		return true;
	return false;
}

bool quinceCmpHeight (const quince q1, const quince q2) {
	if (q1.pos > q2.pos)
		return true;

	return false;
}

int main() {
	unsigned long gmax = 0, minPos, i;
	freopen("gutui.in", "r", stdin);
	freopen("gutui.out", "w", stdout);

	read();

	sort(v.begin(), v.end(), quinceCmpHeight);
	make_heap(heap.begin(), heap.end(), quinceCmpWeight);

	minPos = v[0].pos;
	heap.insert(heap.end(), v[0]);
	push_heap(heap.begin(), heap.end(), quinceCmpWeight);

	for ( i = 1; i < n; i++ ) {
		if ( v[i].pos < v[i-1].pos )
			for ( ; minPos > v[i].pos; minPos-- )
				if(heap.size()) {
					gmax += heap.front().w;
					pop_heap(heap.begin(), heap.end(), quinceCmpWeight);
					heap.pop_back();
				}
		heap.insert(heap.end(), v[i]);
		push_heap(heap.begin(), heap.end(), quinceCmpWeight);
	}
	for ( ; minPos > 0 && heap.size(); minPos-- ) {
		gmax += heap.front().w;
		pop_heap(heap.begin(), heap.end(), quinceCmpWeight);
		heap.pop_back();
	}

	printf("%lu\n", gmax);

	return 0;
}