import java.util.Scanner;


public class Main71 {
	public static void main(String[] args){
		Scanner input = new Scanner(System.in);
		int r= input.nextInt();
		int x= input.nextInt();
		int y = input.nextInt();
		int AFx = input.nextInt();
		int AFy = input.nextInt();
		int distance =(int)Math.ceil(( Math.sqrt((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);
		}
	}
} 
