Problem :

A non-empty zero-indexed 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];
• the successor of a node located at index K is located at index A[K];
• if the value of a node is −1 then it is the last node of the list. For example, for array A such that: A[0] = 1
A[1] = 4
A[2] = -1
A[3] = 3
A[4] = 2
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:
int FindLength (int[] A);
that, given a non-empty zero-indexed 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.

The below are the assumptions that helps you to solve the problem:
• N is an integer within the range [1..200,000];
• each element of array A is an integer within the range [−1..200,000];
• it will always be possible to construct the list and its length will be finite.