import java.util.*;

public class B {
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int rad = sc.nextInt();
		int x = sc.nextInt(), y = sc.nextInt();
		int xp = sc.nextInt(), yp = sc.nextInt();
		double dist = Math.sqrt((x-xp)*(x-xp)+(y-yp)*(y-yp));
		//System.out.println("DIST: " + dist);
		System.out.println(Math.max(((int)dist/rad)-1, 0));
	}
}