import java.util.*;
import java.io.*;
public class Example{
	static class FastReader{
		BufferedReader br;
		StringTokenizer st;

		public FastReader(){
			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;
		}
	}

	public static void main(String[] args) {
		FastReader sc=new FastReader();
	    double r=sc.nextLong();
	    double x=sc.nextLong();
	    double y=sc.nextLong();
	    double x1=sc.nextLong();
	    double y1=sc.nextLong();

	    double dist=Math.sqrt((x-x1)*(x-x1)+(y-y1)*(y-y1));
	    long ans=(long)Math.ceil(dist/(r*2));
	    System.out.println(ans);
           
	}

	
}