Hi can you say me who it's A team

In the books, Mona was the first A, Alison was the second A, and the third A is unknown.

In the show, Mona, Toby, and Spencer were all part of the A Team but now it's just Red Coat and who knows who else. Although, Mona and Hanna both saw Alison in the red coat so it's assumed that she's Red Coat.