import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		AmrAndPins res = new AmrAndPins();
		res.resolve();
	}

	static class AmrAndPins {
		
		public void resolve () {
			Scanner scan = new Scanner(System.in);
			
			double r = scan.nextDouble(), x = scan.nextDouble(), y = scan.nextDouble(),
					x1 = scan.nextDouble(), y1 = scan.nextDouble();
			
			double dis = Math.ceil((Math.sqrt((x-x1)*(x-x1)+(y-y1)*(y-y1)))/(2*r));
			
			System.out.println((long)dis);
		}
		
	}

}