import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        while (cin.hasNext()) {
            int r = cin.nextInt();
            int x = cin.nextInt();
            int y = cin.nextInt();
            int x1 = cin.nextInt();
            int y1 = cin.nextInt();
            double distanced = Math.sqrt((x-x1)*(x-x1)+(y-y1)*(y-y1));
            System.out.println((int)Math.ceil(distanced/(r*2)));
        }
    }
}

