#1 proof in S4

[Anonymous]

I am studying Modal Logic.
So I turned my attention to Molle.
I have tried to prove a theorem in S4
[]...[]A <=> [] A
I wrote: KT4 implies the theorem
( ([](A=>B)=>([]A=>[]B)) & ([]A=> A) & ([]A=>[][]A)) => ([]A<=>[][][][]A)
It does not prove.
What I did wrong?
alvaroanjo@gmail.com

[Nobody/Anonymous]

no_proof