Abstract Algebra, Group Structures question:

For my homework, I have been asked to analyze the following pair of set and binary operation:
N =The set of nonnegative integers, subtraction.

So I'm trying to figure out what the identity is for this set/operation...but I can't think of any.

There must exist some identity element e in N such that for any x in N, e * x = x * e = x, where * is the generic binary operator.

I tried e = 0, but x - 0 is not the same as 0 - x, so this cannot possibly be it... right?

Someone please help

Question

Abstract Algebra, Group Structures question:

For my homework, I have been asked to analyze the following pair of set and binary operation:
N =The set of nonnegative integers, subtraction.

So I'm trying to figure out what the identity is for this set/operation...but I can't think of any.

There must exist some identity element e in N such that for any x in N, e * x = x * e = x, where * is the generic binary operator.

I tried e = 0, but x - 0 is not the same as 0 - x, so  this cannot possibly be it... right?

Someone please help