{2n-1}=ΣA(2i-1) A(2i-1)∩A(2j-1)=φ |A(2i-1)|=4
A(2i-1)={a,b,c,d}
h: a,b,c,d→b,c,d,a
f(a)=f(b)=f(c)=1 f(d)=2
g(a)=b g(b)=c g(c)=d g(d)=2a