import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class Main {
	
	public static void main(String[] args) throws IOException {
		Scanner sc = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		System.out.println(3.2 % 3);
		int r, x, y, a, b;
		r = sc.nextInt();
		x = sc.nextInt();
		y = sc.nextInt();
		a = sc.nextInt();
		b = sc.nextInt();
		
		double dist = Math.sqrt((x - a) * (x - a) + (y - b) * (y - b));
		int res = (int) (dist / (r << 1));
		
		if(dist % (r << 1) != 0)
			res++;
		
		out.println(res);
		
		out.flush();
		out.close();
	}

	static class Scanner{
		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s){	br = new BufferedReader(new InputStreamReader(s));}

		public Scanner(FileReader r){	br = new BufferedReader(r);}

		public String next() throws IOException 
		{
			while (st == null || !st.hasMoreTokens()) 
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}

		public int nextInt() throws IOException {return Integer.parseInt(next());}

		public long nextLong() throws IOException {return Long.parseLong(next());}

		public String nextLine() throws IOException {return br.readLine();}

		public double nextDouble() throws IOException { return Double.parseDouble(next()); }

		public boolean ready() throws IOException {return br.ready();}
	}
}