$ ls -al x/y
ls: cannot access 'x/y': No such file or directory

$ mkdir -p x/y

$ cd x//y

$ pwd
/home/ken/tmp/x/y

$ cd ../..

$ pwd
/home/ken/tmp

$ cd x/y

$ pwd
/home/ken/tmp/x/y

$ cd ../..

$ pwd
/home/ken/tmp