#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

vector<int> bfs(vector<vector<int>> &graph, int s) {
    int INF = numeric_limits<int>::max();
    vector<int> dist(graph.size(), INF);
    queue<int> q;
    dist[s] = 0, q.push(s);
    while(!q.empty()){
        int u = q.front(); q.pop();
        for(int v : graph[u]) if(dist[v] == INF)
            dist[v] = dist[u] + 1, q.push(v);
    }
    return dist;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int N,start,end; cin >> N >> start >> end;
    vector<int> stone(N);
    rep(i,N) cin >> stone[i];
    stone.push_back(start);
    stone.push_back(end);
    N += 2;

    vector<int> V = stone;
    sort(V.begin(), V.end());
    vector<vector<int>> G(N);
    rep(i,N) {
        int u = lower_bound(V.begin(), V.end(), stone[i]) - V.begin();
        rep(b,30) {
            int to = (stone[i] ^ (1 << b));
            if(binary_search(V.begin(), V.end(), to)) {
                int v = lower_bound(V.begin(), V.end(), to) - V.begin();
                G[u].push_back(v);
                G[v].push_back(u);
            }
        }
    }

    start = lower_bound(V.begin(), V.end(), start) - V.begin();
    end = lower_bound(V.begin(), V.end(), end) - V.begin();
    int ans = bfs(G, start)[end];
    cout << (ans == numeric_limits<int>::max() ? -1 : ans - 1) << endl;
}