import java.io.*;
import java.util.*;

public class Solution{ //class Ideone{
 
 
     
     
 public static void main(String[] args) {
     
     Scanner in = new Scanner(System.in);
     
     long r,x,y,x2,y2,dist,ans;
     double a;
     
     r=in.nextLong();
     x=in.nextLong();
     y=in.nextLong();
     x2=in.nextLong();
     y2=in.nextLong();
     
     dist=(x-x2)*(x-x2)+(y-y2)*(y-y2);
     a=Math.sqrt(dist)/(double)(2*r);
     
     ans=(long)Math.floor(a);
     
     if(ans*ans*4*r*r< dist) ans++;
     System.out.println(ans);
     
        
 }
}