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 C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace AtCoder
{
	public class QuestionA
	{
		public static void Main(string[] args)
		{
			// 整数の入力
			int n = int.Parse(Console.ReadLine());

			List<int> buttonList = new List<int>();
			for (int i = 0; i < n; ++i) {
				buttonList.Add(int.Parse(Console.ReadLine()));
			}

			int index = buttonList[0];
			int count = 1;
			while (count <= n) {
				if (index == 2) {
					break;
				}
				++count;
				index = buttonList[index - 1];
			}

			if(count > n) {
				count = -1;
			}

			Console.WriteLine(count);

		}
	}
}