The set of integers Z with the binary operation ∗ defined as a∗b=a+b+1 for a,b,Z is a group. The identity element of this group is
Let S = Z x (Z - {0}) and the binary operation * is defined as (a , b) * (c ,d) = (ad + bc , bd) for all a,b,c,d ϵZ. The identity element of of S for the binary operation * on S is __