#include<stdlib.h>
#include<stdio.h>
typedef struct{
		int height;
		int weight;
		}pom;

void minweight(int a[],int b[],int n1,int n2,int limit){
    int i = n2 -1,j = limit,l = 0;
    int c[n1 + n2]; // defineste mai bine lungimea
    
    while ((j<n1)&&(i>=0)){
      if ((a[j]<b[i]) && (a[j]!=0)) c[l++] = a[j++];
      else 
	c[l++] = b[i--];
    }
    
    for (;j<n1;j++)
      c[l++] = a[j];
    for (;i>=0;i--)
      c[l++] = b[i];
    l--;  
    
    for (i = 0; i<l; i++)
      a[i] = c[i];
      
}
int main(int argc, char * argv[]){
	int n,u,h,aux1,aux2,ind1,ind2,k,l;
	int i,j,x,ind,sum,lung;
	FILE * fis = fopen("gutui.in","r");
	if (fis == NULL) printf("Couldn't open file\n");
	FILE * out = fopen("gutui.out","w");

	fscanf(fis,"%d",&n);
	fscanf(fis,"%d",&h);
	fscanf(fis,"%d",&u);
	
	pom * v = (pom*)malloc(n*sizeof(pom));
	int aux[n];
	int fin[n];
	
	for (i = 0; i<n; i++){
		fscanf(fis,"%d %d",&v[i].height,&v[i].weight);
		}
		
	int ord ;	
	do 	{
		ord  = 0;
		for (i = 0; i<n-1; i++){
			if ((h - v[i].height)%u == 0) ind1 = (h - v[i].height)/u-1;
			else ind1 = (h - v[i].height)/u;
			if ((h - v[i+1].height)%u == 0)ind2 = (h - v[i+1].height)/u-1;
			else ind2 =( h - v[i+1].height)/u;
			
			if (ind1 > ind2 ){
			
			   				 aux1 = v[i+1].height;
							 aux2 = v[i+1].weight;
							 v[i+1].height = v[i].height;
							 v[i+1].weight = v[i].weight;
							 v[i].height = aux1;
							 v[i].weight = aux2;
							 ord  = 1;
							 }
		 else if ((ind1 == ind2)&&(v[i].weight < v[i+1].weight)) {
		 	  				aux1 = v[i+1].height;
							 aux2 = v[i+1].weight;
							 v[i+1].height = v[i].height;
							 v[i+1].weight = v[i].weight;
							 v[i].height = aux1;
							 v[i].weight = aux2;
							 ord  = 1;
		 	  }
							 
		}			   
	}while (ord == 1);
	/*
	for (i = 0; i<n; i++)
		printf("%d %d\n",v[i].height,v[i].weight);
	*/	
	for (i = 0; i<n; i++){
		fin[i] = 0;
	}
	
    	lung = 0;
    	aux1 = 0;
    	
    	
	for (i = 0; i<n; i++){
		if ((h - v[i].height)%u == 0) ind1= (h - v[i].height)/u - 1;
		else ind1 = (h - v[i].height)/u;
		k =  ind1 + 1;
		ind2 =  ind1;
		j = i;
		l = 0;
		aux1 = 0;
		
		while (ind2 == ind1){
			if (k > 0){
				if (v[j].height + u * (lung+aux1) > h)
					if ((v[j].weight > fin[l]) && (fin[l]!=0)) l++;
				aux[aux1++] = v[j].weight;
				k--;
			}
			j++;
			if (j == n-1) break;
			if ((h - v[j].height)%u == 0) ind2= (h - v[j].height)/u - 1;
				else ind2 = (h - v[j].height)/u;
			
		}
		lung = lung + aux1 - l;
		minweight(fin,aux,lung,aux1,l);
		i = j -1;	   				
	}
	
	sum = 0;
	
	for (i = 0; i<lung; i++)
		sum = sum +fin[i];
//	printf("%d\n",sum);
	
	fprintf(out,"%d",sum);
	
	fclose(out);
	fclose(fis);
	return 0;
	
}