police.cpp

// NOTE: it is recommended to use this even if you don't understand the following code.

#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;

int main() {
//  uncomment the following lines if you want to read/write from files
//  ifstream cin("input.txt");
//  ofstream cout("output.txt");
	
	int N, K;
	cin >> N >> K;
	
	int V[N+1];
	for (int i=1; i<=N; i++) {
		cin >> V[i];
	}

	// insert your code here
	int t=0;
	
	if (K == 1) {
		t = 0;
	} else if (count(V, V+N, K) == 0) {
		t = -1;
	} else {
		int h = 1;
		while (h != K) {
			h = V[h];
			t ++;
			if (t == N) {
				t = -1;
				break;
			}
		}
	}
	
	cout << t << endl;  // print the result
	return 0;
}