#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <bitset>
#include <queue>
#include <map>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using mint = modint998244353;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vmi = vector<mint>;
using vvmi = vector<vmi>;
using vvvmi = vector<vvmi>;
#define all(a) (a).begin(), (a).end()
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define rep(i, n) rep2(i, 0, n)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)


int main(){
    int n; cin >> n;
    vi stone(n+2); map<int, int> mp;
    rep(i, n+2){
        cin >> stone[i];
        mp[stone[i]] = i;
    }
    vvi adj(n+2);
    rep(i, n+2){
        bitset<32> bs(stone[i]);
        rep(j, 32){
            bs.flip(j);
            if(mp.count(bs.to_ulong())){
                adj[i].push_back(mp[bs.to_ulong()]);
            }
            bs.flip(j);
        }
    }
    vi dist(n+2, -1);
    dist[0] = 0;
    queue<int> q; q.push(0);
    while(!q.empty()){
        int u = q.front(); q.pop();
        for(auto v : adj[u]){
            if(dist[v] == -1){
                dist[v] = dist[u]+1;
                q.push(v);
            }
        }
    }
    cout << (dist[1] == -1 ? -1 : dist[1]-1) << endl;


    return 0;
}