Intersection

[buran]

So, let's assume the input is as follows:
2
4
1 3 6 9
4
1 2 7 9

I made the change so that you see the full picture

channel1 is busy at 1,2,3,6,7,8,9 and channel2 is busy at 1, 2,7,8,9

what I suggest:

channels_busy = sorted(list(set([1,2,3,6,7,8,9]).intersection(set([1,2,7,8,9]))))
print(channels_busy)

the output will be [1, 2, 7, 8, 9] and you only have to transform it to [1, 2, 7, 9]