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: Accepted)

#include <stdio.h>
int abs(int n){
		if(n<0){
		return -1*n;}else
		return n;}
int main(void)
{int N,A,M,B,x,i,k,l,m,flag,sum;
	scanf("%d",&N);
	int a[100000];
	int b[100000];
	int c[50];
	int d[50];
	int tmp[50];
	b[0]=1;
	flag=0;
	for(i=0;i<=N-1;i++){
		scanf("%d",&a[i]);}
	
	for(x=0;x<=N-1;x++){
		b[x+1]=a[b[x]-1];}
	for(k=1;k<=N;k++){
		if(b[k]==2){
			flag=1;
			sum=k;
			break;}}
if(flag==1)
printf("%d",k);
else
printf("-1");



	return 0;
}