Unique Words Checker (Case Insensitive)

Given a list of words, determine whether all the words are unique when compared in a case insensitive manner. In other words, two words that differ only by letter case (for example, Hello and hello) are considered equal.

The input begins with an integer n which denotes the number of words. The next line contains n words separated by spaces. If n = 0, the list is considered empty.

Your task is to print YES if all words are unique after converting them to lowercase or NO if there is any duplicate.

Note: Use standard input and output for reading and printing.

For example, given the input:

4
python Java C++ Rust

After converting all words to lowercase (python, java, c++, rust), there are no duplicates and the output should be:

YES

inputFormat

The first line contains one integer n (n ≥ 0) indicating the number of words. The second line contains n words separated by spaces.

outputFormat

Output a single line containing YES if all words are unique (case insensitive), and NO otherwise.

## sample

4
python Java C++ Rust

YES

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