#include<stdio.h>
#include<stdlib.h>
int functie(int *v,int N,int *gr){
	int min,max=0;
	int i;
	min=v[0];
	for(i=0;i<N;i++)
	if (v[i]<min) min=v[i];
	for(i=0;i<N;i++)
	if (v[i]==min) 
		if (gr[i]>max) max=gr[i];
		return max;  
}

int minim(int *v,int N){
	int min, i;
	min=v[0];
	for(i=0;i<N;i++)
	if (v[i]<min) min=v[i];
	return min;    }
	
 	
	int main(){
    int N,H,U;
    int v[100],k=0;
	int high[100],gr[100];
	int d,l=0;
	int h1[100];
	int i,x,s=0;
	FILE *f;
	FILE *g; 
    f=fopen("gutui.in","r");
	g=fopen("gutui.out","w");
	fscanf(f,"%d\t",&N);
	fscanf(f,"%d\t",&H);
	fscanf(f,"%d\n",&U);
	for (i=0;i<N;i++){
	fscanf(f,"%d\t",&high[i]);
	fscanf(f,"%d\n",&gr[i]);}
    for(i=0;i<N;i++)
    h1[i]=high[i];
	
	for(i=0;i<N;i++){ s=0;
   	 while (h1[i]<H){
     s=s+1;
     h1[i]=h1[i]+U; }
   	 v[k++]=s;}
   	 

      
     v[l++]=functie(v,N,gr);
      
    
	
	fclose(f);
	fclose(g);
	return 0;
}