
import java.util.*;
public class Amrandpins {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

		Scanner input = new Scanner(System.in);
		int r = input.nextInt();
		int x = input.nextInt();
		int y = input.nextInt();
		int x1 = input.nextInt();
		int y1 = input.nextInt();
		double z = Math.sqrt((x-x1)*(x-x1) + (y-y1)*(y-y1));

		System.out.println((int)(Math.ceil(z/(2*r))));
				
	}

}
