Switzerland has four official languages: principally German (63.5% total population share, with foreign residents, in 2013); French (22.5%) in the west; and Italian (8.1%) in the south. The fourth official language, <answer>Romansh</answer> (0.5%), is a Romance language spoken locally in the southeastern trilingual canton of Graubünden, and is designated by Article 4 of the Federal Constitution as a national language along with German, French, and Italian, and in Article 70 as an official language if the authorities communicate with persons who speak <answer>Romansh</answer>. However, federal laws and other official acts do not need to be decreed in <answer>Romansh</answer>.
What is the least popular official language of Switzerland?
Romansh