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 9.2.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9 + 5;
int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	int n = INF;
	cin >> n;
	int ans = 1;
	int nums[n];
	for(int i = 0;i<n;++i)
		cin >> nums[i];	
	int curr = nums[0];
	bool yes = false;
	for(int i=1;i<n;i++) {
		if(nums[curr] == 2) {
			cout << ans << '\n';	
			yes = true;
		}
		if(nums[curr] == 0)
			curr = 0;
		else
			curr = nums[curr-1];
		ans++;
	}	
	if(!yes)
		cout << -1 << '\n';
}