https://programmers.co.kr/learn/courses/30/lessons/68935?language=cpp

int solution(int n) {
	int answer = 0;
	string num;
	while (n > 0) {
		num.push_back((n % 3 + '0'));
		n /= 3;
	}
	int three = 1;
	for (int i = num.size() - 1; i >= 0; i--) {
		answer += (num[i] - '0') * three;
		three *= 3;
	}

	return answer;
}