public static class ClothingSizeCalculator
{
    public static int CalculateSize(string gender, int heightCm, int chestCm)
    {
        int baseSize = (chestCm / 2) - 6;
        gender = gender.ToLower();

        if (gender == "frau"  gender == "female"  gender == "w")
        {
            if (heightCm > 170)   return baseSize * 2;
            if (heightCm < 164)   return baseSize / 2;
        }

        return baseSize;
    }
}
