#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll,ll>;
#define rep(i, n) for(ll i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    vector<int> a(n-1);
    rep(i,n-1){
        cin >> a[i];
        a[i]--;
    }
    vector<ll> dist(n,1001001001);
    dist[0] = 0;
    queue<int> que;
    que.push(0);
    while(que.size()){
        int now = que.front();
        que.pop();
        if(chmin(dist[a[now]], dist[now]+1)) que.push(a[now]);
    }
    if(dist[n-1]==1001001001) dist[n-1] = -1;
    cout << dist[n-1] << '\n';
    return 0;
}