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

public class Main{


    public static void main(String[] args) throws IOException{
        Reader sc = new Reader();
        PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out), true);
        
        long r = sc.nextLong();
        long x = sc.nextLong();
        long y = sc.nextLong();
        long xx = sc.nextLong();
        long yy = sc.nextLong();

        double d = Math.sqrt(((x-xx)*(x-xx))+((y-yy)*(y-yy)));
       // System.out.println((int)d);
        d/=(2*r);
        d = Math.ceil(d);

        System.out.println((int)d);




        
    }





    
}




/*Reader class*/
class Reader {
        BufferedReader br;
        StringTokenizer st;
 
        public Reader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }
 
        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
 
        int nextInt() { return Integer.parseInt(next()); }
        long nextLong() { return Long.parseLong(next()); }
        double nextDouble() { return Double.parseDouble(next()); }
         
        String nextLine(){
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }