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

public class Codeforces{
	
	static class MyScanner{
		BufferedReader br;
		StringTokenizer st;
		
		MyScanner(){
			br = new BufferedReader(new InputStreamReader(System.in));
		}
		
		String nn(){
			while(st == null || !st.hasMoreElements()){
				try{
					st = new StringTokenizer(br.readLine());
				}catch(IOException e){
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}
		
		int ni(){
			return Integer.parseInt(nn());
		}
		
		long nl(){
			return Long.parseLong(nn());
		}
		
		double nd(){
			return Double.parseDouble(nn());
		}
	}
	
	private static PrintWriter out;
	
	public static void main(String[] args) throws CloneNotSupportedException{
		
		MyScanner sc = new MyScanner();
		out = new PrintWriter(new BufferedOutputStream(System.out));
		
		int r = sc.ni(), x1 = sc.ni(), y1 = sc.ni(), x2 = sc.ni(), y2 = sc.ni();
		
		double dist = Math.sqrt((double)Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));
		
		long ans = (long)Math.ceil(dist / (2 * r));
		
		out.println(ans);
		
		out.close();
	}
}