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

public class Main {
	private static InputReader ir;
	private static PrintWriter out;
	
	public static void main(String[] args) {
		ir = new InputReader(System.in);
		out = new PrintWriter(System.out);
		
		int r = ir.nextInt();
		int x1 = ir.nextInt();
		int y1 = ir.nextInt();
		int x2 = ir.nextInt();
		int y2 = ir.nextInt();
		
		Double distance = Math.sqrt(Math.pow((x1 - x2), 2) + Math.pow((y1 - y2), 2));
		
		out.println((int) Math.ceil(distance / (2 * r)));
		out.flush();
	}
	
	static class InputReader {
		public BufferedReader reader;
		public StringTokenizer tokenizer;

		public InputReader(InputStream stream) {
			reader = new BufferedReader(new InputStreamReader(stream), 32768);
			tokenizer = null;
		}

		public String next() {
			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					tokenizer = new StringTokenizer(reader.readLine());
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
			}
			return tokenizer.nextToken();
		}

		public int nextInt() {
			return Integer.parseInt(next());
		}
	}
}