
import java.util.Scanner;


/**
 *
 * @author nferes
 */
public class JavaApplication23 {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
         Scanner in = new Scanner(System.in);
         int R= in.nextInt();
         int x1= in.nextInt();
         int y1= in.nextInt();
         int x2= in.nextInt();
         int y2= in.nextInt();
         
         double m3= Math.sqrt((x2-x1)*(x2*x1) +(y2-y1)*(y2-y1));
         double d = Math.ceil(m3/(2*R));
         
         System.out.println((int)d);
         System.out.println();
         
                  // TODO code application logic here
    }
    
}
