n = input()
ans = int(n)

chack = True
while chack:
	for i in range(len(n)):
		if n[i] == "3":
			ans2 = ans//pow(10, len(n)-i-1)
			ans = int(ans2)*pow(10, len(n)-i-1)-1
			n = str(ans)
	if ans%3 != 0:
		for i in range(len(n)):
			chack = False
			if n[i] == "3":
				chack = True
	else:
		ans -= 1

print(ans)