Delete a listindex with an IF compnent

Hello

I hope someone can undestand my problem:
I create a serie of 12 numbers. From an other source i got the value of my listlenght (IT can be 12 or 11) If i got the input of 12, the serie can rest like she is (a serie of 12 numbers) but if the input is 11 ( i wanted to delet the middle position of the serie)
The question is: HOW can i create a solution with an IF Compotent. Like if is true, go forrward with my list of 12 indexes, but if it`s not clear the middle value, to get 11 values, and go forrward with that one!

thx for any help ( i hope with the attaked image, it´s more clear)