Unique Character Counter

You are given a string s. Your task is to count the number of unique characters in the string, treating uppercase and lowercase letters as the same (i.e. the comparison is case-insensitive).

For example, if s = "Hello123", then converting all letters to lowercase gives "hello123", and the set of unique characters is { h, e, l, o, 1, 2, 3 }, so the answer is 7.

Please note that all characters (including digits and symbols) should be considered.

inputFormat

The input consists of a single line containing the string s.

You can assume that the length of s is at most 10,000 characters.

outputFormat

Output a single integer: the number of distinct characters in the string after converting all alphabetical characters to lowercase.

Hello123

7