I am attempting to use nested ifs without success. Hows the situation:

Three cells (a1,a2,a3) will contain the values of true/false. Two will be fasle and 1 true.

I have coded the following statement:
=if(a1=true,"Team A"); if(a2=true, "Team B"); "Tie")
I get a 508 err.
What is my coding error?
Thanks.