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 Pascal (FPC 2.6.2) (judge verdict: Accepted)

const MaxN=round(1e5)+10;
var A:array[0..MaxN] of longint;
    n,res:longint;

procedure nhap;
var i:longint;
begin

    readln(n);
    for i:=1 to n do
        readln(a[i]);
end;

procedure xuli;
var x:longint;
begin
    x:=1;res:=0;
    repeat
        x:=a[x];
        inc(res);
        if x=2 then
        begin
            writeln(res);
            halt;
        end;
    until res>n;
end;
procedure xuat;
begin
    writeln(-1);

end;

begin
    nhap;
    xuli;
    xuat;
end.