Let N be the set of natural numbers and two functions f and g be defined as f, g : N N such that
f(n) = \left\{ {\matrix{
{{{n + 1} \over 2};} & {if\,\,n\,\,is\,\,odd} \cr
{{n \over 2};} & {if\,\,n\,\,is\,\,even} \cr
} \,\,} \right.;
and g(n) = n ( 1)^n.
Then fog is -