import java.util.Scanner;


public class Main71 {
	public static void main(String[] args){
		Scanner input = new Scanner(System.in);
		long r= input.nextLong();
		long x= input.nextLong();
		long y = input.nextLong();
		long AFx = input.nextLong();
		long AFy = input.nextLong();
		long distance =(long)Math.ceil(( Math.sqrt((AFx-x) * (AFx-x) + (AFy-y) * (AFy-y))));
//		System.out.println(distance);
//		System.out.println(Math.sqrt((AFx-x) * (AFx-x) + (AFy-y) * (AFy-y)));
////		long temp = +  ;
//		System.out.println((AFx-x) * (AFx-x) + " " + (AFy-y) * (AFy-y));
		if(distance % (r*2) != 0){
			System.out.println(distance / r/2 +1);
		}
		else{
			System.out.println(distance/r/2);
		}
	}
} 
