import java.io.*;
import java.util.*;
public class b287{
   public static void main(String[] args) {
      MyScanner obj = new MyScanner();
      long r=obj.nextLong();
      long x=obj.nextLong();
      long y=obj.nextLong();
      long x1=obj.nextLong();
      long y1=obj.nextLong();
      
      
      double d1=Math.sqrt((Math.pow(x1-x,2))+(Math.pow(y1-y,2)));
      int ans=(int)Math.ceil(d1/(r*2));
	  System.out.println(ans);
      
}
   
   public static class MyScanner {
      BufferedReader br;
      StringTokenizer st;
 
      public MyScanner() {
         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;
      }

   }
}
