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

#define MAXX 100001

typedef struct DATE {
	unsigned long int a;
	unsigned long int b;
	} date;
	
date in[MAXX];
date out[MAXX];

void merge(int low, int high, int mid) {
	int i, j, k;
	unsigned long int c[MAXX],d[MAXX];
	i=low;
	j=mid+1;
	k=low;
	while((i<=mid)&&(j<=high)) { 
		if (in[i].a > in[j].a) {
			c[k]=in[i].a;
			d[k]=in[i].b;
			k++;
			i++;
		}
		else {
			c[k]=in[j].a;
			d[k]=in[j].b;
			k++;
			j++;
		}
	}
	while(i <= mid) {
		c[k]=in[i].a;
		d[k]=in[i].b;
		k++;
		i++;
	}
	while(j<=high){
		c[k]=in[j].a;
		d[k]=in[j].b;
		k++;
		j++;
	}
	for(i=low;i<k;i++) {
		in[i].a=c[i];
		in[i].b=d[i];
	}
} 



void mergesort( int low, int high) {
	int mid;
	if(low<high) {
		mid=(low+high)/2;
		mergesort(low,mid);
		mergesort(mid+1,high);
		merge(low,high,mid);
	}
}

int main () {
	
	FILE *f,*g;
	f=fopen("gutui.in","r");
	g=fopen("gutui.out","w");
	unsigned long int n,h,u; 
	fscanf (f, "%lu %lu %lu",&n,&h,&u);
	char c[100];
	fgets(c,MAXX,f); // sa ajung pe urm linie
	int i,j;
	
	unsigned long int gmax=0; // greutatea maxima
	
	for (i=0;i<n;i++)
		fscanf (f, "%lu %lu",&in[i].a,&in[i].b);	

	
	mergesort(0,n-1);

	int k = 0; //contor pt a numara cate elem voi avea in out
	for (i = 0; i < n;i ++ )
		if (in[i].a <= h) {
			out[k].a = in[i].a;
			out[k].b = in[i].b;
			gmax += in[i].b; 			 
			h -= u ; 
			k++;
		}
		else {
			int pozmin=0;
			for (j=1;j<k;j++) {				
				if (out[j].b < out[pozmin].b ) 
					pozmin=j;
			}			
			if (k !=0)
				if ( in[i].b > out[pozmin].b ) { 				
					gmax =gmax + in[i].b - out[pozmin].b;
					out[pozmin].a = in[i].a;
					out[pozmin].b = in[i].b;
				}
		}
	fprintf(g, "%lu\n",gmax);
		
		
	return 0;
}