input:
-3 3
2 2 1 2 2 1
output:
2

your test is wrong 'cause A must be >=0

This tests can help you:

1 3
2 2 1 2 2 1
1

1 3
1 1 2 2 2 1
1

I think, that your test's are not correct.Second line must contain f(1),f(2),f(3) and no more.

Try tests:

1 9
1 2 1 2 3 2 1 2 1
4

1 10
1 2 1 2 1 0 1 2 1 2
5

1 7
1 2 1 2 1 0 1
5

My solution is greedy. One boolean, one counter and list of nonrecurring array of numbers, but i think, that we can work with numbers during reading.
Nice problem :)

> 1 7
> 1 2 1 2 1 0 1
> 5
How can that be true? (1, 2), (1, 2), (1, 0), (1) - this means, that answer should be 4.