import java.util.Scanner;

public class test {
	public static void main(String[] args) {
		Scanner sc =new Scanner(System.in);
		String[] split =sc.nextLine().split(" ");
		int r = Integer.parseInt(split[0]);
		int x = Integer.parseInt(split[1]);
		int y = Integer.parseInt(split[2]);
		int x1 = Integer.parseInt(split[3]);
		int y1 = Integer.parseInt(split[4]);

		double length = Math.sqrt((x-x1)*(x-x1) + (y-y1)*(y-y1));
		int d = 2 * r;
		double a = length / d;

		if(a % 1 == 0) {
			System.out.println((int)(a/1));
		} else {
			System.out.println((int)(a/1) + 1);
		}
	}
}
    	 	  		 				  	 				 	  			