# -*- coding: utf-8 -*-

def simple(n, N):
	""" TLEします """
	sum_sheep = 0
	for i in range(1,N+1):
		sum_sheep += i
		if sum_sheep < n:
			continue
		elif sum_sheep == n:
			print("YES")
			print(i)
			exit()
		else:
			print("NO")
			exit()

def sum_one_to_n(n, N):
	""" 1からnまでの和 = n*(n+1)/2 の公式使ったもの"""
	if n == 1:
		print("OK")
		print("1")
		exit()
	for i in range(2, N+1):
		sum_sheep = i*(i+1)/2
		if sum_sheep < n:
			continue
		elif sum_sheep == n:
			print("OK")
			print(i)
			exit()
		else:
			print("NG")
			exit()

if __name__ == "__main__":
	n = int(input())
	N = 2*(10**18)
	sum_one_to_n(n, N)