import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int r = s.nextInt();
		int x = s.nextInt();
		int y = s.nextInt();
		int xn = s.nextInt();
		int yn = s.nextInt();
		int count = 0;
		double distance = Math.pow(Math.pow(xn-x, 2) + Math.pow(yn-y, 2),0.5);
		while(distance>2*r){
			distance = distance-(2*r);
			count++;
		}
		if(xn==x && yn==y){
			System.out.println(count);
			return;
		}
		
		System.out.println(count+1);
	}

}