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.io.IOException;
import java.util.Scanner;
public class Main {
	static int mod=1000000007;
	static Scanner scan=new Scanner(System.in);
	static long gcd (long a, long b) {return b>0?gcd(b,a%b):a;}
	static long lcm (long a, long b) {return a*b/gcd(a,b);}
	static int max(int a,int b) {return a>b?a:b;}
	static int min(int a,int b) {return a<b?a:b;}
	static long factorial(int i) {return i==1?1:i*factorial(i-1);}
	static int lower_bound(int a[],int key) {
		int low=0,high=a.length;
		while(low<high) {
			int mid=((high-low)/2)+low;
			if(a[mid]<=key)low=mid+1;
			else high=mid;
		}
		return high;
		}
	static int upper_bound(int a[],int key) {
		int low=0,high=a.length;
		while(low<high) {
			int mid=((high-low)/2)+low;
			if(a[mid]<key)low=mid+1;
			else high=mid;
		}
		return high;
		}
	static boolean isPrime (int n) {
		if (n==2) return true;
		if (n<2 || n%2==0) return false;
		double d = Math.sqrt(n);
		for (int i=3; i<=d; i+=2)if(n%i==0){return false;}
		return true;
	}
	static int upper_division(int a,int b) {
		if(a%b==0) {
			return a/b;
		}
		else {
			return a/b+1;
		}
	}
	static long lupper_division(long a,long b) {
		if(a%b==0) {
			return a/b;
			}
		else {
			return a/b+1;
		}
	}
	static long lmax(long a,long b) {return Math.max(a, b);}
	static long lmin(long a,long b) {return Math.min(a, b);}
	static int[] setArray(int a) {
		int b[]=new int[a];
		for(int i=0;i<a;i++) {
			b[i]=scan.nextInt();
		}
		return b;
	}
	static String reverce(String str) {
		String strr="";
		for(int i=str.length()-1;i>=0;i--) {
			strr+=str.charAt(i);
		}
		return strr;
	}
	static long modpow(long a,long n) {
		if(n==0) return 1;
		else if(n==1)return a;
		long tmp=modpow(a,n/2);
		tmp%=mod;
		tmp*=tmp;
		tmp%=mod;
		if(n%2==0)return tmp;
		else return (tmp*a)%mod;
	}
	public static void main(String[] args) throws IOException {
		int a[]=setArray(scan.nextInt());
		int cnt=1;
		int now=0;
		for(int i=0;i<a.length;i++,cnt++) {
			if(a[now]==2) {
				System.out.println(cnt);
				return;
			}
			now=a[now]-1;
		}
		System.out.println(-1);
	}
}