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

public class B
{
   public static void main(String[] args) throws Exception
   {
      PrintWriter out = new PrintWriter(System.out);
      new B(new FastScanner(System.in), out);
      out.close();
   }

   public B(FastScanner in, PrintWriter out)
   {
      int r = in.nextInt()*2;
      int x1 = in.nextInt();
      int y1 = in.nextInt();
      int x2 = in.nextInt();
      int y2 = in.nextInt();
   
      double dx = x1-x2;
      double dy = y1-y2;
      double d = Math.sqrt(dx*dx+dy*dy)-1e-9+r;
      double times = d/r;
      out.println((long)times);
   }
}

class FastScanner{
    private InputStream stream;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;
    
    public FastScanner(InputStream stream)
    {
        this.stream = stream;
    }
    
    int read()
    {
        if (numChars == -1)
            throw new InputMismatchException();
        if (curChar >= numChars){
            curChar = 0;
            try{
                numChars = stream.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0)
                return -1;
        }
        return buf[curChar++];
    }
    
    boolean isSpaceChar(int c)
    {
        return c==' '||c=='\n'||c=='\r'||c=='\t'||c==-1;
    }
    
    boolean isEndline(int c)
    {
        return c=='\n'||c=='\r'||c==-1;
    }
    
    int nextInt()
    {
        return Integer.parseInt(next());
    }
    
    long nextLong()
    {
        return Long.parseLong(next());
    }
    
    double nextDouble()
    {
        return Double.parseDouble(next());
    }
    
    String next(){
        int c = read();
        while (isSpaceChar(c))
            c = read();
        StringBuilder res = new StringBuilder();
        do{
            res.appendCodePoint(c);
            c = read();
        }while(!isSpaceChar(c));
        return res.toString();
    }
    
    String nextLine(){
        int c = read();
        while (isEndline(c))
            c = read();
        StringBuilder res = new StringBuilder();
        do{
            res.appendCodePoint(c);
            c = read();
        }while(!isEndline(c));
        return res.toString();
    }
}
