import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.StringTokenizer;

public class Solution2 {
	public static void main(String[] args){
		 	FastReader sc = new FastReader();
		 	int r = sc.nextInt();
		 	int x1 = sc.nextInt();
		 	int y1 = sc.nextInt();
		 	int x2 = sc.nextInt();
		 	int y2 = sc.nextInt();
		 	System.out.println((int)(Math.ceil((Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2))/(2 * r)))));
	}
	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;
        }
    }
}