Problem:
Score : 200 points

Problem Statement

Takahashi wants to gain muscle, and decides to work out at AtCoder Gym.

The exercise machine at the gym has N buttons, and exactly one of the buttons is lighten up.
These buttons are numbered 1 through N.
When Button i is lighten up and you press it, the light is turned off, and then Button a_i will be lighten up. It is possible that i=a_i.
When Button i is not lighten up, nothing will happen by pressing it.

Initially, Button 1 is lighten up. Takahashi wants to quit pressing buttons when Button 2 is lighten up.

Determine whether this is possible. If the answer is positive, find the minimum number of times he needs to press buttons.

Constraints

2 ≤ N ≤ 10^5

1 ≤ a_i ≤ N

Input

Input is given from Standard Input in the following format:

N
a_1
a_2
:
a_N

Output

Print -1 if it is impossible to lighten up Button 2.
Otherwise, print the minimum number of times we need to press buttons in order to lighten up Button 2.

Sample Input 1

3
3
1
2

Sample Output 1

2

Press Button 1, then Button 3.

Sample Input 2

4
3
4
1
2

Sample Output 2

-1

Pressing Button 1 lightens up Button 3, and vice versa, so Button 2 will never be lighten up.

Sample Input 3

5
3
3
4
2
4

Sample Output 3

3

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;
import java.util.stream.IntStream;

public class Main{
	static final Scanner s=new Scanner(System.in);
	static IntStream REPS(int v){
		return IntStream.range(0,v);
	}
	static IntStream INS(int n){
		return REPS(n).map(i->getInt());
	}
	static int getInt(){
		return Integer.parseInt(s.next());
	}
	
	public static void main(String[]__){
		int n=getInt(),b[]=INS(n).toArray();
		boolean[]sh=new boolean[n];
		
		int i=0,c=0;
		while(true){
			if(sh[i])break;
			sh[i]=true;
			if(i==1)break;
			i=b[i]-1;
			c++;
		}
		
		System.out.println(sh[1]?c:-1);
	}
}