import java.util.*;
public class xyz{
	public static void main(String s[]){
		Scanner sc = new Scanner(System.in);
		int r = sc.nextInt();
		int x = sc.nextInt();
		int y = sc.nextInt();
		int x1 = sc.nextInt();
		int y1 = sc.nextInt();
		double ans = Math.pow(x1-x,2) + Math.pow(y1-y,2);
		int ans1 = (int)Math.ceil(Math.sqrt(ans));
		int result = ans1/(2*r);
		if(ans1%(2*r)!=0){
			result+=1;
		}
		System.out.println(result);
	}
}