static Dictionary<char, int> CountCharsInStr2(string str)
        {
            int[] intArr = {'a', 'A', 'z', 'Z'};
            var arr = new int[intArr.Max() + 1];
            for (var i = 0; i < str.Length; i++) arr[str[i]]++;
            var result = new Dictionary<char, int>(('z' - 'a') + ('Z' - 'A') + 2);
            for (int i = 'a'; i <= 'z'; i++) result[(char) i] = arr[i];
            for (int i = 'A'; i <= 'Z'; i++) result[(char) i] = arr[i];
            return result;
        }