Score : $200$ points
There are $N$ people, called Person $1$, Person $2$, $\ldots$, Person $N$.
The parent of Person $i$ $(2 \le i \le N)$ is Person $P_i$. Here, it is guaranteed that $P_i < i$.
How many generations away from Person $N$ is Person $1$?
Input is given from Standard Input in the following format:
$N$ $P_2$ $P_3$ $\dots$ $P_N$
Print the answer as a positive integer.
3 1 2
2
Person $2$ is a parent of Person $3$, and thus is one generation away from Person $3$.
Person $1$ is a parent of Person $2$, and thus is two generations away from Person $3$.
Therefore, the answer is $2$.
10 1 2 3 4 5 6 7 8 9
9