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.util.Scanner;

class Main {

    String Name;
    int V;
    boolean T;

    Main(String Name, int V, boolean T) {
        this.Name = Name;
        this.V = V;
        this.T = T;
    }

    public static void main(String[] args) {
        Scanner Input = new Scanner(System.in);
        int N = Input.nextInt();
        Main A[] = new Main[N];
        for (int I = 0; I < N; I++) {
            A[I] = (new Main("B" + I, Input.nextInt() - 1, false));
        }
        int C = 1;
        boolean TF = false;
        int X = A[0].V;
        A[0].T = true;
        while (!TF) {

            if (A[X].Name.equals("B1")) {
                System.out.println(C);
                TF = true;
            } else if (A[X].T) {
                System.out.println("-1");
                TF = true;
            }

            A[X].T = true;
            X = A[X].V;
            C++;
        }

    }

}
//<<< Copying >>> Alert
//If(PersonCopy){System.out.print("You Are Not Learning");