abc065-B.cpp

#include <bits/stdc++.h>  

using namespace std;

#define FOR(i, j, k) for(int i = j; i < k; ++i)
#define rep(i, j) FOR(i, 0, j)
#define FORr(i, j, k) for(int i = j; i >= k; --i)
#define repr(i, j) FOR(i, j, 0)
#define INF (1 << 30)

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;
typedef pair<P, int> Pi;

const int MOD = 1e9 + 7;
const int dy[]={0, 0, 1, -1};
const int dx[]={1, -1, 0, 0};

template <class T> void chmin(T& a, const T& b) { a = min(a, b); }
template <class T> void chmax(T& a, const T& b) { a = max(a, b); }

int a[100001];
bool went[100001];

int main() {
	int N;
	scanf("%d", &N);
	rep(i, N) scanf("%d", &a[i]);
	int now = 1, cnt = 0;
	while(1) {
		if(went[now]) {
			printf("-1\n");
			return 0;
		}
		if(now == 2) break;
		went[now] = true;
		now = a[now - 1];
		++cnt;
	}
	printf("%d\n", cnt);
	return 0;
}