Unique Words Count

You are given a sentence consisting of alphabetic words separated by spaces. Your task is to count the number of unique words in the sentence. The comparison should be case-insensitive, meaning that words such as Apple and apple are considered identical.

In formal terms, given a string \( S \), let \( W \) be the set of words extracted from \( S \) after converting all characters to lowercase. The answer is \( |W| \), the cardinality of this set.

Example:

Input:  Hello world
Output: 2

inputFormat

The input is provided via standard input (stdin) as a single line containing a sentence. A sentence is a sequence of words made up of alphabetic characters separated by spaces.

outputFormat

The output should be written to standard output (stdout) as a single integer representing the count of unique words.

## sample

Hello

1

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