The answer should be with 10^-2 accuracy.
But keep in mind that we do not accept extra zeroes.
1 != 1.0 != 1.00
1.1 != 1.10

But what does 'extra zeros' mean?
For example, if the accurate value is 6.0004, shall I output 6 or 6.00?
And what if 6.000000000000004, which is just floating-point error?

Just 6, in both cases.

for C++, it would be a troublesome

cout<<setiosflags(ios::fixed)<<setprecision(2)<<result<<endl;

the program above will not work
so I have to write a void to do it myself.