Average Numbers In Sequence

I have cells O1 to O300 numbers in random sequences of no more than 10

I need to average the 5 highest numbers in each sequence eg:

O P
1 2 16 (result)
2 20
3 4
4 6
5 14
6 12
7 8
8 10
9 16
10 18
11 blank cell
12 15 9 (result)
13 3
14 6
15 12
16 9
17 blank cell
18 blank cell
19 4 23 (result)
20 16
21 20
22 40
23 8
24 11
25 28
26 blank cell

down to 300 rows, the sequence of numbers can be from 1 to 10 but never
more than 10

I got a function : =IF(COUNT(O1:O10>=10,AVERAGE(LARGE(O1:O10,{1,2,3,4,5})),"
") but that works only for 10 numbers and not for less