import java.io.*;
import java.util.*;
public class b287{
   public static void main(String[] args) {
      MyScanner obj = new MyScanner();
      int r=obj.nextInt()*2;
      int x=obj.nextInt();
      int y=obj.nextInt();
      int x1=obj.nextInt();
      int y1=obj.nextInt();
      int ans=0;
      int x2=(x1-x)*(x1-x);
      int y2=(y1-y)*(y1-y);
      double d=Math.sqrt(x2+y2);
      int d1=(int)Math.sqrt(x2+y2);
      if(d1%r==0&&d==(double)d1)
		ans=d1/r;
      else 
		ans=(d1/r)+1;
	  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;
      }

   }
}
