Dom't worry,next year the question being changed to f(f(x))=n+ 2

We can get f=n+1006.HA.

There is no linear f, it is easy. Let f=cx+d,fof=c(cx+d)+d=x+2011. We get c=1,d=2011/2.

d out of range,no solution.

For any f also no solution,only ralation can canstruct.