import java.util.*;
import java.io.*;
import static java.lang.Math.*;
import static java.util.Arrays.*;
public class Main {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);

		try {
			long r = in.nextLong();
			long x = in.nextLong();
			long y = in.nextLong();
			long xx = in.nextLong();
			long yy = in.nextLong();

			out.println((long)(ceil(hypot(x - xx, y - yy) / 2 / r)));

		} finally {
			out.flush();
		}
	}
}
