# import sys; input = sys.stdin.buffer.readline
# sys.setrecursionlimit(10**7)
# from collections import defaultdict
# con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	N = int(input())
	for i in range(33):
		if N == 2 ** i - 1:
			print("X")
			return

	print("O")




if __name__ == '__main__':
	main()