import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main{
	static class Escanner{
		BufferedReader in;
		StringTokenizer st;
		Escanner(){
			in = new BufferedReader(new InputStreamReader(System.in));
			st = new StringTokenizer("");
		}
		int nextInt() throws IOException{
			if(st.hasMoreTokens())
				return Integer.parseInt(st.nextToken());
			st = new StringTokenizer(in.readLine());
			return nextInt();
		}
	}

	static double ed(int x1, int y1, int x2, int y2){
		return Math.sqrt( ((x1-x2)*(x1-x2)) + ((y1-y2)*(y1-y2)) );
	}
	
	public static void main (String[] args) throws IOException{
		Escanner sc = new Escanner();
		int r = sc.nextInt();
		double d = ed(sc.nextInt(), sc.nextInt(), sc.nextInt(), sc.nextInt());
		System.out.println( (int)Math.ceil(d/(2*r)) );

	}
}