
import java.math.BigInteger;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.PriorityQueue;
import java.util.Scanner;
import java.util.Set;





public class Main {
 

  
    
    public static void main(String[] args) {
        
   
    
    
       
        Scanner sc=new Scanner(System.in);
      
        int r=sc.nextInt();
        int x1=sc.nextInt();
        int y1=sc.nextInt();
        int x2=sc.nextInt();
        int y2=sc.nextInt();
               
       int step=0;
      
       double dist;
       dist= Math.sqrt(Math.pow(x1-x2,2)+Math.pow(y1-y2, 2));
       // System.out.println(dist);
       step+=Math.ceil( dist/(2*r));
     
                System.out.println(step);
}
}
