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

public class B {
	public static void main(String[] args) throws IOException {
		BufferedReader f = new BufferedReader(new InputStreamReader(System.in));
		Scanner s = new Scanner(System.in);
		
		double r = s.nextDouble(), x1 = s.nextDouble(), y1 = s.nextDouble(), x2 = s.nextDouble(), y2 = s.nextDouble();
		double dist = dist(x1, y1, x2, y2);
		System.out.println((int)(Math.ceil(dist / (2*r))));
	}
	
	static double dist(double x1, double y1, double x2, double y2) {
		return Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
	}
}