import java.util.*;
public class cf507B {
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
long r=sc.nextLong();
long x1=sc.nextLong();
long y1=sc.nextLong();
long x2=sc.nextLong();
long y2=sc.nextLong();
double d=Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
System.out.println((long)Math.ceil(d/(2*r)));sc.close();        
    }
}