Count Unique Words

Your task is to write a program that reads a string from standard input and outputs the number of unique words contained in it. A word is defined as a maximal substring of non-space characters. The comparison of words should be case-insensitive, meaning that words differing only in letter case are considered the same.

For example:

• The input This is a test This test is should return 4 because there are 4 unique words: "this", "is", "a", "test".
• The input one one ONE one should return 1.

Note: Ensure that your solution reads input from standard input (stdin) and writes the result to standard output (stdout).

inputFormat

The input consists of a single line containing a string s. The string may include spaces, and its length can be zero.

outputFormat

Output a single integer representing the number of unique words in the given string. Words are compared in a case-insensitive manner.

This is a test This test is

4