import java.io.*;
import java.util.*;
public final class Codeforces
{
     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[]) throws IOException
    {
      FastReader sc=new FastReader();
     int r=sc.nextInt();
     int x1=sc.nextInt();
     int y1=sc.nextInt();
     int x2=sc.nextInt();
     int y2=sc.nextInt();
     double d=distance(x1,y1,x2,y2);
     double x=(d/(2*r));
     System.out.println((int)Math.ceil(x));
     
    }
    static double distance(int x1, int y1, int x2, int y2) 
{ 
    // Calculating distance 
    return Math.sqrt(Math.pow(x2 - x1, 2) +  
                Math.pow(y2 - y1, 2) * 1.0); 
} 
    }
