B'A company has n employees numbered from 1 to n. Each employee either has no immediate manager or exactly one immediate manager, who is another employee with a different number. An employee A is said to be the superior of another employee B if at least one of the following is true: The company will not have a managerial cycle. That is, there will not exist an employee who is the superior of his/her own immediate manager. Today the company is going to arrange a party. This involves dividing all n employees into several groups: every employee must belong to exactly one group. Furthermore, within any single group, there must not be two employees A and B such that A is the superior of B. What is the minimum number of groups that must be formed? The first line contains integer n (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xe2 x80 x89 xe2 x89 xa4 xe2 x80 x892000) -- the number of employees. The next n lines contain the integers pi (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89pi xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n or pi xe2 x80 x89= xe2 x80 x89-1). Every pi denotes the immediate manager for the i-th employee. If pi is -1, that means that the i-th employee does not have an immediate manager. It is guaranteed, that no employee will be the immediate manager of him/herself (pi xe2 x80 x89 xe2 x89 xa0 xe2 x80 x89i). Also, there will be no managerial cycles. Print a single integer denoting the minimum number of groups that will be formed in the party. For the first example, three groups are sufficient, for example: '...