임시 공부용

map<int, int> m;

void sub(long long i) {
	if(m[i] == 0) return i;
	return m[i] = sub(i+1);
}

vector<long long> solution(long long k, vector<long long> room_number)
{
    vector<long long> answer;
    for(int i=0; i<room_number.size(); i++) {
    	if(m[i] == 0) {
    		answer.push_back(i)
    		m[i] = sub(i+1);
    	}
    	else {
    		long long tmp = sub(i);
    		answer.push_back(tmp);
    		m[tmp] = sub(tmp+1);
    	}
    }
    
	return answer;
}