import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Set;
import java.util.StringTokenizer;


public class Main{

    
   
   
    static class FastScanner{
        BufferedReader s;
        StringTokenizer st;
        
        public FastScanner(){
            st = new StringTokenizer("");
            s = new BufferedReader(new InputStreamReader(System.in));
        }
        
        public FastScanner(File f) throws FileNotFoundException{
            st = new StringTokenizer("");
            s = new BufferedReader (new FileReader(f));
        }
        
        public int nextInt() throws IOException{
            if(st.hasMoreTokens())
                return Integer.parseInt(st.nextToken());
            else{
                st = new StringTokenizer(s.readLine());
                return nextInt();
            }
        }
        
        public double nextDouble() throws IOException{
            if(st.hasMoreTokens())
                return Double.parseDouble(st.nextToken());
            else{
                st = new StringTokenizer(s.readLine());
                return nextDouble();
            }
        }
        
        public long nextLong() throws IOException{
            if(st.hasMoreTokens())
                return Long.parseLong(st.nextToken());
            else{
                st = new StringTokenizer(s.readLine());
                return nextLong();
            }
        }
        
        public String nextString() throws IOException{
            if(st.hasMoreTokens())
                return st.nextToken();
            else{
                st = new StringTokenizer(s.readLine());
                return nextString();
            }
            
        }
        public String readLine() throws IOException{
            return s.readLine();
        }
        
        public void close() throws IOException{
            s.close();
        }
        
    }

           static FastScanner s = new FastScanner();   
           static PrintWriter ww = new PrintWriter(new OutputStreamWriter(System.out));
            public static void main (String[] args) throws Exception{
          //FastScanner s = new FastScanner(new File("input.in")); 
          //PrintWriter ww = new PrintWriter(new FileWriter("output.txt"));
                Main ob=new Main();
                ob.solve();
                s.close();
                ww.close();
            }
            void solve() throws IOException
            {
            int n=s.nextInt();
            int x1=s.nextInt();
            int y1=s.nextInt();
            int x2=s.nextInt();
            int y2=s.nextInt();
            double distance = Math.sqrt(Math.pow(Math.abs(x2 - x1), 2) + Math.pow(Math.abs(y2 - y1), 2));
            int ans=(int)Math.ceil(distance / (2 * n));
            ww.printf("%d",ans);
            ww.println();
            }
}