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: Wrong Answer)


import java.util.Scanner;

public class Main {

	public static void main(String[] args) throws Exception {
		//BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		//String line = br.readLine();
		Scanner scan = new Scanner(System.in);


	    int[] button = new int[1000000];
	    button[0] = scan.nextInt();
	    for(int j=1;j<button[0];j++)
	    	button[j]=scan.nextInt();
	    int count = 0;

	    for(int i=1;button[i]==0;i=i+0)
	    	if(button[i]!=0)
	    	{
	     		count++;
	     		if(button[i]==2)
	     			System.out.println(count);
	     		else
	     		{
	     			button[i]=0;
	    	continue;
	    	    }
	     		
	        }
	    	else
	    		System.out.println("-1");


	}
	
	}