import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;
import java.util.StringTokenizer;
import java.lang.*;
public class Main
{
     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) {
		FastReader sc= new FastReader();
        long r=sc.nextLong();
        long x1=sc.nextLong();
        long y1=sc.nextLong();
        long x2=sc.nextLong();
        long y2=sc.nextLong();
        double s=Math.sqrt((x1-x2)*(x1-x2) +
                            (y1-y2)*(y1-y2) );
        long x=(long)(s/(2*r));
        if(s/(2*r)!=(long)(s/(2*r)))
        {x++;}
        System.out.println(x);
        
	}
}