import java.util.*;
import java.io.*;
import java.lang.*;
public class Main{ 
    
    public static void main(String[] args) throws Exception{
        FastScanner sc =new FastScanner();
        PrintWriter out=new PrintWriter(System.out);
        int r=sc.nextInt(),x=sc.nextInt(),y=sc.nextInt(),a=sc.nextInt(),b=sc.nextInt();
        double d=Math.sqrt((x-a)*(x-a)+(y-b)*(y-b));        
        out.println((long)Math.ceil(d/(2*r)));
        out.close();

    }
}

class FastScanner{
    BufferedReader br =new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st =new StringTokenizer("");
    String next(){
        if(!st.hasMoreTokens()){
            try{
                st=new StringTokenizer(br.readLine());
            }
            catch(Exception e){    
            }
        }
        return st.nextToken();
    }
    int nextInt(){
        return Integer.parseInt(next());
    }
}