A triangular number is the number of dots in an equilateral triangle uniformly filled with dots. For example, three dots can be arranged in a triangle; thus three is a triangular number. The n-th triangular number is the number of dots in a triangle with n dots on a side. <image>. You can learn more about these numbers from Wikipedia (http://en.wikipedia.org/wiki/Triangular_number).

Your task is to find out if a given integer is a triangular number.

Input

The first line contains the single number n (1 ≤ n ≤ 500) — the given integer.

Output

If the given integer is a triangular number output YES, otherwise output NO.

Examples

Input

1


Output

YES


Input

2


Output

NO


Input

3


Output

YES



import java.util.Arrays;
import java.util.Scanner;


public class JavaApplication37 {
   
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int []a=new int [35];
        for(int i=0;i<35;i++){
            a[i]=(i+1)*i/2;
        }
        boolean f=false;
             for(int i=0;i<35;i++){
                 if(n==a[i]){
                     System.out.println("YES");
                     f=true;
                     break;
                 }
                
             }
              if(!f)System.out.println("NO");
            }}   