import java.util.*;
import java.lang.*;
import java.io.*;



/* Name of the class has to be "Main" only if the class is public. */



public class Main
{
     
     
     
    static PrintWriter out;
    
	static class FastReader{
		BufferedReader br;
		StringTokenizer st;
		public FastReader(){
			br=new BufferedReader(new InputStreamReader(System.in));
			out=new PrintWriter(System.out);
		}
		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;
		}
	}
	

// SHIVAM GUPTA :



// ASCII = 48 + i ;

static Set<Character> set1  ; static Set<Character> set2  ;


public static boolean isPossibleTriangle(int a  ,int b , int c)
{
      if( a + b > c && c+b > a && a +c > b)
      {
            return true  ;
      }
      
      return false  ;
      
      
}
    
   
    
public static void main (String[] args) throws java.lang.Exception
{
  FastReader scn = new FastReader() ;
  
long r = scn.nextInt() ;long xo = scn.nextInt() ;long yo = scn.nextInt() ;
long xn = scn.nextInt() ;long yn = scn.nextInt() ;


  double d=  (xo-xn)*(xo-xn) + (yo-yn)*(yo-yn) ;

         d = Math.pow(d,0.5);
        
        
        long ans = (long)Math.ceil(d/(2*r)) ;
        
        out.println(ans) ;


      
out.flush() ;  
  
}


}
  
 