A non-empty array A consisting of N integers is given.

Array A represents a linked list. A list is constructed from this array as follows:

the first node (the head) is located at index 0;
the value of a node located at index K is A[K];
if the value of a node is −1 then it is the last node of the list;
otherwise, the successor of a node located at index K is located at index A[K] (you can assume that A[K] is a valid index, that is 0 ≤ A[K] < N).

For example, for array A such that:

A[0] = 1 A[1] = 4 A[2] = -1 A[3] = 3 A[4] = 2

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the following list is constructed:

the first node (the head) is located at index 0 and has a value of 1;
the second node is located at index 1 and has a value of 4;
the third node is located at index 4 and has a value of 2;
the fourth node is located at index 2 and has a value of −1.

Write a function:

def solution(A)

that, given a non-empty array A consisting of N integers, returns the length of the list constructed from A in the above manner.

For example, given array A such that:

A[0] = 1 A[1] = 4 A[2] = -1 A[3] = 3 A[4] = 2

the function should return 4, as explained in the example above.

Assume that:

N is an integer within the range [1..200,000];
each element of array A is an integer within the range [−1..N-1];
it will always be possible to construct the list and its length will be finite.

I read this question and still don't understand why the order of list in that way. Would you please explain? Could not post a photo here to make it easier to understand. Thank you so much!