Treatment of buta-\( 1,3 \)-diyne with \( \mathrm{NaNH_2} \) (\( 2 \) equivalents), followed by reaction with excess of trans–\( \mathrm{CH_3-CH=CH-CH_2-Br} \) gives \( X \) as the major product. The maximum number of carbon atoms that are collinear (in a straight line) in \( X \) is ______.
