public static long getTime(int difficulty, int i) {
        if (instance == null) {
            return Long.MIN_VALUE;
        }
        switch (difficulty) {
            case Grid.DIFFICULTY_EASY: return instance.easyTime[i];
            case Grid.DIFFICULTY_MEDIUM: return instance.mediumTime[i];
            case Grid.DIFFICULTY_HARD: return instance.hardTime[i];
            case Grid.DIFFICULTY_EXTREME: return instance.extremeTime[i];
            default: return Long.MIN_VALUE;
        }
    }