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

public class Practice {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] s = br.readLine().split(" ");
        int r = Integer.parseInt(s[0]);
        int x = Integer.parseInt(s[1]);
        int y = Integer.parseInt(s[2]);
        int xf = Integer.parseInt(s[3]);
        int yf = Integer.parseInt(s[4]);
        double d = Math.sqrt(Math.abs(Math.pow(xf-x, 2))+Math.abs(Math.pow(yf-y, 2)));
        // System.out.println(d);
        System.out.println((int)(Math.ceil(d/(2*r))));
    }
}