len ()
in
x.add (& lt؛ elem & gt؛)
x
& lt؛ elem & gt؛
x.remove (& lt؛ elem & gt؛)
& lt؛ elem & gt؛ & nbsp؛
x.discard (& lt؛ elem & gt؛)
x.pop ()
x.clear ()
1000 ms 256 Mb Rules for program design and list of errors in automatic problem checking