description of output is not clearly enough,
I think i have WA11 because of it
what should  i output for such test?
2
a 3
b 2
3
x
a
z

But what is a real answer for this test?

Answer should be:
[empty line]
a
[empty line]

I had WA11 becouse I handled multiple equal queries incorrectly

My AC prog writes:
a
[empty line]

2admins: please dont' rejudge it :)
you have to describe output format more clear

Alias why you had WA11?

try this
3
a
aa
aaa
1
a