import java.util.*;
public class Tester
{
	public static void main(String[] args) 
	{
		Scanner s = new Scanner(System.in);
		
		int r=s.nextInt();
		int x=s.nextInt();
		int y=s.nextInt();
		int x1=s.nextInt();
		int y1=s.nextInt();
		
		long temp=((long)y-(long)y1)*((long)y-(long)y1)+((long)x-(long)x1)*((long)x-(long)x1);
		double dis=Math.sqrt(temp);
		//System.out.println(dis);
		
		int moves=(int)Math.ceil((double)dis/(2*r));
		System.out.println(moves);
	}
}
