[Решено] Add custom way to show the language switcher to header

Background of the issue:
At the header, I have added the shortcode that is given from WPML for the language switcher. I don't want to show the whole word of the language but instead the country code (for example, English to become EN and Greek to become GR).

Symptoms:
N/A

Questions:
How can I modify the language switcher to display country codes instead of full language names? (e.g English = EN, Greek = GR)