class TrigonometricSeries {

    public static TrigonometricSeries regular(int periodicity) {
        int n = periodicity / 2;
        double[] freq = new double[n];
        double f = 2.0 / periodicity;
        for (int i = 1; i <= n; ++i) {
            freq[i - 1] = f * i;
        }
        return new TrigonometricSeries(freq);
    }

    public  TrigonometricSeries(double[] freq);

}