import java.util.Arrays;
import java.util.Scanner;
import java.lang.Math;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int r = sc.nextInt();
		int x = sc.nextInt();
		int y = sc.nextInt();
		int x2 = sc.nextInt();
		int y2 = sc.nextInt();
		double dist = Math.sqrt((Math.pow(x2-x,2)+Math.pow(y2-y,2)));
		//System.out.println(dist);
		int cont = 0;
		int i;
		while(dist>0){
			dist-=r+r;
			cont++;
		}
		System.out.println(cont);
	}
}

 	   			  				    	 	 		 	  	 	