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

#define NMAX 100001

long int minim (long int v[NMAX], int i, int j) {
	if (i == j) return i;
	long int a, b, m;
	m = (i+j)/2;
	a = minim (v, i, m); b = minim (v, m+1, j);
	return (v[a] > v[b]) ? b : a;
}

int main () {

FILE *f, *g;
long int n, hmax, u, h, val, s=0, i, j, v[NMAX];


f = fopen ("gutui.in", "r");
g = fopen ("gutui.out", "w");

fscanf (f, "%ld", &n);
fscanf (f, "%ld", &hmax);
fscanf (f, "%ld", &u);

long int index = 0;

for (i=1; i<=n; i++) {
	fscanf (f, "%ld", &h);
	fscanf (f, "%ld", &val);
	j = (hmax-h)/u + 1;
	if (j > index) {
		index++;
		v[j] = val;
		s += val;
	}
	else {
		long int k = minim (v, 1, j);
		if (val > v[k]) {
			s = s-v[k]+val;
			v[k] = val;
		}
	}
}






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

fclose (f); fclose (g);

return 0;
}