#include <bits/stdc++.h>
#include <atcoder/all>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace atcoder;
using namespace __gnu_pbds;
using ll=long long;
using ld=long double;
using vll=vector<ll>;
using vvll=vector<vll>;
using pll=pair<ll,ll>;

// using mint=modint;

// template<class K,class V>
// using ordered_map=tree<K,V,less<K>,rb_tree_tag,tree_order_statistics_node_update>;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

    ll N;
    cin>>N;
    vll stone(N+2);
    for(int i=0;i<N+2;++i)cin>>stone[i];

    unordered_map<ll,ll>id;
    for(int i=0;i<N+2;++i)id[stone[i]]=i;

    vll d(N+2,-1);
    queue<ll>q;
    d[0]=0;
    q.push(0);
    while(!q.empty()){
        ll u=q.front();
        ll y=stone[u];
        q.pop();
        for(int b=0;b<30;++b){
            ll x=y^(1LL<<b);
            if(id.count(x)){
                ll v=id[x];
                if(d[v]==-1){
                    d[v]=d[u]+1;
                    q.push(v);
                }
            }
        }
    }

    if(d[1]==-1)cout<<-1<<endl;
    else cout<<d[1]-1<<endl;

}