#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> P;

int hammingDistance(int a, int b) {
  int x = a ^ b;
  int res = 0;
  while (x > 0) {
    res += x & 1;
    x >>= 1;
  }
  return res;
}

int main() {
  int n, start, end;
  cin >> n >> start >> end;
  
  vector<int> stones(n);
  vector<bool> visited(n);
  for (int i=0; i<n; ++i) {
    cin >> stones[i];
    visited[i] = false;
  }

  map<int, vector<int>> weights;
  for (int i=0; i<n; ++i) {
    int weight = hammingDistance(0, stones[i]);
    weights[weight].push_back(i);
  }

  queue<P> que;
  que.push(P(0, start));
  
  while (!que.empty()) {
    P p = que.front();
    que.pop();

    if (hammingDistance(p.second, end) == 1) {
      cout << p.first << endl;
      return 0;
    }

    int weight = hammingDistance(0, p.second);
    // weight-1
    for (int i: weights[weight-1]) {
      if (visited[i]) {
        continue;
      }
      if (hammingDistance(p.second, stones[i]) == 1) {
        visited[i] = true;
        que.push(P(p.first+1, stones[i]));
      }
    }
    // weight+1
    for (int i: weights[weight+1]) {
      if (visited[i]) {
        continue;
      }
      if (hammingDistance(p.second, stones[i]) == 1) {
        visited[i] = true;
        que.push(P(p.first+1, stones[i]));
      }
    }
  }
  cout << "-1" << endl;
  return 0;
}