import java.io.*;
import java.util.*;

public class two{
	public static void main(String[] args)throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.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 distance = Math.pow(Math.pow(y1-y,2) + Math.pow(x1-x,2),0.5);
		distance =  Math.ceil(distance);

		double movements = distance/(r * 2);
		movements = Math.ceil(movements);
		System.out.println((int)movements);
	}
}