import java.util.*;
import java.math.*;

public class Main{
	public static void main(String[] args) {
	    
		Scanner s = new Scanner(System.in);
        int raio = s.nextInt();
        int eixoX = s.nextInt();
        int eixoY = s.nextInt();
        int eixoX2 = s.nextInt();
        int eixoY2 = s.nextInt();
        double distancia = Math.sqrt( Math.pow(eixoX2 - eixoX, 2) + Math.pow(eixoY2 - eixoY, 2) );
        double answer = Math.ceil(distancia / (2 * raio));
        System.out.println(String.format("%.0f", answer));
	}
}
					   			 	 		   				  					