Revert "23_Advanced_Operators reviewed"

This reverts commit 9d6ba8c25cb3e209260d0d8e278fab36bc9dc159.
Merge remote-tracking branch 'upstream/master'
merge upsteam/master
Revert "Revert "23_Advanced_Operators reviewed""

This reverts commit 60aeb233d2dd1382fda0f051e0dcb260394fe064.
Merge pull request #1 from trans4fun/master

merge from upstream
Revert "merge upsteam/master"

This reverts commit 06306118d57fd9f6f859226e6a752858f82c7108.
delete english part
Merge pull request #94 from MrSunny/master

Delete english part