import java.util.Scanner;

public class AmrAndPins {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        double r = in.nextDouble();
        double x = in.nextDouble();
        double y = in.nextDouble();
        double xdash = in.nextDouble();
        double ydash = in.nextDouble();
        double distance = Math.sqrt(Math.pow(xdash - x, 2) + Math.pow(ydash - y, 2));
        double count = 1;
        while(distance > (count*2*r)){
            count++;
        }
        if(distance == 0){
            System.out.println(0);
        } else {
            System.out.println((int)count);
        }
    }
}
