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

public class Main {

	static BufferedReader br = new BufferedReader(new InputStreamReader(
			System.in));
	static PrintWriter out = new PrintWriter(new BufferedOutputStream(
			System.out));
	static StringTokenizer st = new StringTokenizer("");

	public static String next() {
		try	{
		while (!st.hasMoreTokens()) {
			String s = br.readLine();
			if (s == null)
				return null;
			st = new StringTokenizer(s);
		}
		return st.nextToken();
		}	catch(Exception e)	{
			return	null;
		}
	}
	public static void main(String[] asda) throws Exception {

        int r = Integer.parseInt( next() );
        long x = Integer.parseInt( next() );
        long y = Integer.parseInt( next() );
        long xx = Integer.parseInt( next() );
        long yy = Integer.parseInt( next() );
        
        x = (xx - x);
        x *= x;
        
        y = (yy - y);
        y *= y;
        
        double dist = Math.sqrt(x + y);
        long d = (long)Math.ceil( dist / (r * 2));
        d = Math.max(d, 0);
        
        out.println(d);
        
        //
        out.flush();
        System.exit(0);
    }
}