Editorial for Mock CCC '19 Contest 1 S1 - Pusheen's Report Card
Submitting an official solution before solving the problem yourself is a bannable offence.
This problem is a homage to CCC 2018 S1, which tripped up competitors who had trouble with rounding.
The two intended solutions were to use the standard rounding mechanism built-in to the languages, or to compute the average exactly and then print it properly.
For the subtask of ~N=1~, it sufficed to print
.0 after the only mark.
For the subtask of ~N=10~, one could print the sum of all marks, divided by 10, followed by a decimal point, followed by the remainder of the above division.