import java.util.*;
public class amr {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner scan = new Scanner(System.in);
		long r = scan.nextInt();
		long x = scan.nextInt();
		long y = scan.nextInt();
		long x1 = scan.nextInt();
		long y1= scan.nextInt();
		long distance = (x1-x) * (x1-x) + (y1-y) * (y1-y);
		double ans = Math.sqrt(((double) distance)/4/r/r);
		if(ans == Math.round(ans)){
			System.out.println(Math.round(ans));
		}
		else{
			System.out.println((int) ans + 1);
		}
	}

}
