C++ 백준 17204번 죽음의 게임

#include<iostream>
#include<vector>
using namespace std;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	int N, K;
	int ans = 0;
	cin >> N >> K;
	
	vector<int> a(N);
	
	for (int i = 0; i < N; i++)
	{
		cin >> a[i];
	}
	int temp;
	vector<bool> vi(N);
	temp = a[0];
	while (vi[temp] != true)
	{
		ans++;
		vi[temp] = true;
		if (temp == K)
		{
			cout << ans  << endl;
			return 0;
		}
		temp = a[temp];
		
	}
	cout << "-1" << endl;
	
	return 0;


}