# [Haskell], <s>80</s> 66 bytes

<!-- language-all: lang-hs -->

    map(!"1a2b3c4d5e6f7g8h9i0j")
    e!(a:b:y)|e==a=b|e==b=a|1<2=e!y
    e!_=e

[Try it online!][TIO-jj7l9zoc]

[Haskell]: https://www.haskell.org/
[TIO-jj7l9zoc]: https://tio.run/##Fcy9DsIgFEDh3acA4tAOTQTrX@N9ClcTc8FbQGlDCg5N@uxinc7wJcdhelMIxcK9DBgrLiQqvTft80DH/mTP7uJ3L1FviFfY6W6uFwJA0P9owEVeFRCfV38ArQs/MmDxk295YltmmcjOJ58w5cmPVkrVivI1fUCbSmNi/AE "Haskell – Try It Online"