[I'm entering my comment above as an answer here, so as to stop this question being bumped to the front page in the future.]
There is simply a typo: the definition of $f_u^{cp}(\gamma)$ should be $\gamma + u$(etc. ...).
[I'm entering my comment above as an answer here, so as to stop this question being bumped to the front page in the future.]
There is simply a typo: the definition of $f_u^{cp}(\gamma)$ should be $\gamma + u$(etc. ...).