import java.util.Scanner;
import java.util.*;
public class B11
{

	public static void main(String[] args) 
	{
		Scanner sc = new Scanner(System.in); 
		
		int r=sc.nextInt();
		int x1=sc.nextInt();
		int y1=sc.nextInt();
		int x2=sc.nextInt();
		int y2=sc.nextInt();
		
		
		double dist = Math.sqrt( (x1-x2)*(x1-x2) + (y1-y2)*(y1-y2) );
		double ans = Math.ceil(dist/(2*r)) ;
		
	
			
		System.out.println((int)ans);
	}

}

