
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Pins {

    public static void main(String[] args) throws IOException {

        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String[] strings = reader.readLine().split(" ");
        int r = Integer.valueOf(strings[0]);
        int x = Integer.valueOf(strings[1]);
        int y = Integer.valueOf(strings[2]);
        int x2 = Integer.valueOf(strings[3]);
        int y2 = Integer.valueOf(strings[4]);
        System.out.println((long)Math.ceil(Math.sqrt(Math.pow(x2 - x, 2) + Math.pow(y2 - y, 2)) / (r * 2)));

    }
}
