import java.util.Scanner;

public class B507 {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        long r = input.nextInt()*2;
        long x1 = input.nextInt();
        long y1 = input.nextInt();
        long x2 = input.nextInt();
        long y2 = input.nextInt();
        long dx = x1-x2;
        long dy = y1-y2;
        double d = Math.sqrt(dx*dx+dy*dy);
        int answer = (int)Math.ceil(d/r);
        System.out.println(answer);
    }

}