#include<bits/stdc++.h>
using namespace std;
const int mod=1e9+7;
int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int N;
  cin>>N;
  int from,to;
  cin>>from>>to;
  vector<int>A(N);
  for(int &i:A)cin>>i;
  A.push_back(from),A.push_back(to);
  sort(A.begin(),A.end());
  unordered_map<int,int>to_idx;
  array<int,2>sg={0,0};
  for(int i=0;i<N+2;i++){
    if(A[i]==from){
      sg[0]=i;
    }
    if(A[i]==to){
      sg[1]=i;
    }
    to_idx[A[i]]=i;
  }
  vector<int>dist(N+2,1e9);
  vector<vector<int>>G(N+2);
  for(int i=0;i<N+2;i++){
    for(int j=0;j<30;j++){
      if(to_idx.find(A[i]^(1<<j))!=to_idx.end()){
        G[i].push_back(to_idx[A[i]^(1<<j)]);
      }
    }
  }
  queue<int>bfs;
  dist[sg[0]]=0;
  bfs.push(sg[0]);
  while(bfs.size()){
    int v=bfs.front();
    bfs.pop();
    for(int i:G[v]){
      if(dist[i]>dist[v]+1){
        dist[i]=dist[v]+1;
        bfs.push(i);
      }
    }
  }
  cout<<(dist[sg[1]]==1e9?-1:dist[sg[1]]-1)<<'\n';
}