import java.util.*;
import java.io.*;

public class circle {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int radius = scanner.nextInt();
        int x1 = scanner.nextInt(), y1 = scanner.nextInt();
        int x2 = scanner.nextInt(), y2 = scanner.nextInt();
        double dist = Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
        System.out.println((int)(Math.ceil(dist / (2 * radius))));
    }
}
