class AuthenticationManager { // https://leetcode.com/problems/design-authentication-manager/
private:
    unordered_map<string, int> users;
    multiset<int> times;
    int ttl = 0;
public:
    AuthenticationManager(int timeToLive) {
        ttl = timeToLive;
    }

    void generate(string tokenId, int currentTime) {
        this->users[tokenId] = currentTime + this->ttl;
        this->times.insert(currentTime + this->ttl);
    }

    void renew(string tokenId, int currentTime) {
        auto prev = this->users[tokenId];
        this->users[tokenId] = currentTime + this->ttl;
        this->times.erase(this->times.find(prev));
    }

    int countUnexpiredTokens(int currentTime) {
        auto range = this->times.upper_bound(currentTime);
        return distance(this->times.begin(), range) - 1;
    }
};