import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Scanner;

public class Solution {
    public static void main (String[] args) {
        Scanner in = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
        int r = in.nextInt();
        int x = in.nextInt();
        int y = in.nextInt();
        int x2 = in.nextInt();
        int y2 = in.nextInt();
        System.out.println((int) Math.ceil(Math.sqrt(Math.pow(x - x2, 2) + Math.pow(y - y2, 2)) / (r * 2.0)));
        in.close();
    }
}