import java.util.*;
public class Main {

	public static void main(String[] args) {
		Scanner cin = new  Scanner(System.in);
		int r = cin.nextInt();
		int x1 = cin.nextInt();
		int y1 = cin.nextInt();
		int x2 = cin.nextInt();
		int y2 = cin.nextInt();
		int tx = x1 - x2, ty = y1 - y2;
		double dis = Math.sqrt((double)(tx * tx + ty * ty));
		//System.out.println(dis);
		double res = Math.ceil((dis / ((double)2 * r)));
		System.out.println((long)res);
	}

}
