import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class Main{

	public static void main(String[] args) throws IOException {
		BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
		PrintWriter pw = new PrintWriter(new OutputStreamWriter(System.out));

		StringTokenizer st = new StringTokenizer(bf.readLine());
		int r = Integer.parseInt(st.nextToken());
		int x = Integer.parseInt(st.nextToken());
		int y = Integer.parseInt(st.nextToken());
		int x1 = Integer.parseInt(st.nextToken());
		int y1 = Integer.parseInt(st.nextToken());

		double d = Math.sqrt(Math.pow(x1 - x, 2) + Math.pow(y1 - y, 2));
		int res = (int) Math.ceil(d / (2 * r));

		pw.write(String.valueOf(res));
		pw.flush();
	}
}