6824.Company Queries I

Time Limit: 1s Memory Limit: 512MB

A company has $n$ employees, who form a tree hierarchy where each employee has a boss, except for the general director.

Your task is to process $q$ queries of the form: who is employee $x$ 's boss $k$ levels higher up in the hierarchy?

Input Format(From the terminal/stdin)

The first input line has two integers $n$ and $q$ : the number of employees and queries. The employees are numbered $1,2,\dots,n$ , and employee $1$ is the general director.

The next line has $n-1$ integers $e_2,e_3,\dots,e_n$ : for each employee $2,3,\dots,n$ their boss.

Finally, there are $q$ lines describing the queries. Each line has two integers $x$ and $k$ : who is employee $x$ 's boss $k$ levels higher up?

  • $1 \le n,q \le 2 \cdot 10^5$
  • $1 \le e_i \le i-1$
  • $1 \le x \le n$
  • $1 \le k \le n$

Output Format(To the terminal/stdout)

Print the answer for each query. If such a boss does not exist, print $-1$ .

Sample Input

Copy
5 3
1 1 3 3
4 1
4 2
4 3
 · \n
 · · · \n
 · \n
 · \n
 · \n

Sample Output

Copy
3
1
-1
 \n
 \n
  \n
Source: CSES, Tree Algorithms, 1687

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