How could I do like this in an efficitent way in PyTorch?

Input X and Y:

X = [1,2,3,4,5,6,7,8, 9, 10, 11, 12]

Y = [77, 88, 99]

I want to get a vector like this:

Z = [1,2,3,4, 77, 5, 6,7,8, 88, 9, 10, 11, 12, 99]

I want to insert a elelemt from Y into X after 4 elements of X, how to do it in an efficient way?

Thanks in advance.