#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, st, ed, v;
    cin >> n >> st >> ed;
    vector<int> S(n);
    for(auto &&v:S)cin >> v;
    S.push_back(st);
    S.push_back(ed);
    S.push_back(1 << 30);
    sort(S.begin(), S.end());
    S.erase(unique(S.begin(), S.end()), S.end());
    vector<int> dist(S.size(), 1 << 30);
    queue<int> nxt;
    v = lower_bound(S.begin(), S.end(), st) - S.begin();
    nxt.push(v);
    dist[v] = 0;
    while(!nxt.empty()){
        v = nxt.front();
        nxt.pop();
        for(int i = 0; i < 30; i++){
            int to = S[v] ^ (1 << i);
            int j = lower_bound(S.begin(), S.end(), to) - S.begin();
            if(to == S[j] && dist[j] > dist[v] + 1){
                dist[j] = dist[v] + 1;
                nxt.push(j);
            }
        }
    }
    ed = lower_bound(S.begin(), S.end(), ed) - S.begin();
    if(dist[ed] >> 30 & 1)dist[ed] = 0;
    cout << dist[ed] - 1 << '\n';
}