Now,assume that you have two choice,αandβ
you choose one and don't let your pair know
if you choose αand your pair choose α,both of you get 0;
if you choose αand your pair choose β,you get 3 and your pair gets -1;
if you choose βand your pair choose β,both of you get 1
if you choose βand your pair choose α,you get -1 and your pair gets 3;
what is your choice?