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 JavaScript (node.js v5.12) (judge verdict: Accepted)

process.stdin.resume();
process.stdin.setEncoding('utf8');
 
// inputに入力データ全体が入る
function Main(input) {
  // 1行目がline1, 2行目がline2, …に入る
  var tmp = input.split("\n");
  var line0 = tmp[0].split(" ");
  //var line1 = tmp[1].split(" ");
  //var line2 = tmp[2].split(" ");
  //var line3 = tmp[3].split(" ");

  var n = Number(line0[0]);
  var ans = "hoge";

  //console.log(n +" "+ " " + " hoge ")

  var count = 0;
  for(var i=1; i<=n; i ){
    //console.log(tmp[i]);
    count++;
    i=tmp[i];
    //console.log( "i="+ i + ", count="+count);

    if(i==2) break;
    if(count == n) {
      count = -1;
      break;
    }

  }  
  console.log(count);

}
//*この行以降は編集しないでください（標準入出力から一度に読み込み、Mainを呼び出します）
Main(require("fs").readFileSync("/dev/stdin", "utf8"));