import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;
import java.util.*;
 
public class Minimise {
    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 java.lang.Exception
	{
		// your code goes here
	
		FastReader sc = new FastReader();
    	
        long r = sc.nextInt();
        long x = sc.nextInt();
        long y = sc.nextInt();
        long xx = sc.nextInt();
        long yy= sc.nextInt();
        System.out.println((int)Math.ceil(Math.sqrt((x-xx)*(x-xx)+(y-yy)*(y-yy))/(2*r)));}}
       // System.out.println((int)(Math.ceil(Math.sqrt((x1-x)*(x1-x)+(y1-y)*(y1-y))/(2*r))));