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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<stdlib.h>
#pragma warning(disable:4996)
#include<string.h>
#include<ctype.h>
int main()
{
	long long n,a[100003];
	int f[100003]={1};
	long long i,s,count=0;
	scanf("%lld",&n);
	for(i=1;i<=n;i++)
	{
		scanf("%lld",&a[i]);
		f[i]=1;
	}
	f[1]=0;
	s=a[1];
	count++;
	while(1)
	{
	if(f[s]!=0)
	{
		f[s]=0;
		s=a[s];
		count++;
	}
	if(s==2)break;
	if(s=a[s])break;
		
	}
	if(s==2)printf("%lld",count);
	else printf("-1");
	return 0;
	
}