import java.util.*;
import java.io.*;
public class amr_pins
{

	public static void main(String[] args) throws FileNotFoundException
	{
		//File inFile = new File("input.txt");
		Scanner inScan = new Scanner(System.in);
		
		int radius = inScan.nextInt();
		int x = inScan.nextInt();
		int y = inScan.nextInt();
		int x_prime = inScan.nextInt();
		int y_prime = inScan.nextInt();
		
		
		System.out.println((int)(Math.ceil(calcDistance(x,y,x_prime,y_prime) / (2*radius))));
		
		
	}
	
	public static double calcDistance(int x, int y, int x_prime, int y_prime)
	{
		return Math.sqrt(Math.pow(x-x_prime,2) + Math.pow(y-y_prime,2));
	}

}