# [Python 2], 108 bytes

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

    i=input().split(".")[::-1]
    for x in range((1,2)[ord(i[0][0])<91],len(i)):i[x]=i[x][0]
    print".".join(i[::-1])

[Try it online!]

[Python 2]: https://docs.python.org/2/
[Try it online!]: https://tio.run/nexus/python2#JczBCgIhFIXh/TyFuPLCdMl2Dc2qV2gnLmQyuWVeUYN5ezOCw9n88HVaKeVPU4A1R2pKogSzLAdtpwcXsQtKorgUvFJ6PoHhcldkjnYMLmdt5@iTIoCFzG7X340y5UKpDQqfTCP/QehdbvzGwByix8hDLZjd9nLB483Xdo2uVvkF "Python 2 – TIO Nexus"