#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <limits.h>
#include <map>
#include <queue>
#include <set>
#include <string.h>
#include <vector>

using namespace std;
typedef long long ll;
const int MAX_N = 50010;

struct Node {
  int v;
  int dist;

  Node(int v = -1, int dist = -1) {
    this->v = v;
    this->dist = dist;
  }
};

int main() {
  int N;
  cin >> N;
  int start, end;
  cin >> start >> end;

  bool exists[MAX_N];
  memset(exists, false, sizeof(exists));
  exists[start] = true;
  exists[end] = true;

  for (int i = 0; i < N; ++i) {
    int s;
    cin >> s;
    exists[s] = true;
  }

  queue<Node> que;
  que.push(Node(start, 0));
  bool visited[MAX_N];
  memset(visited, false, sizeof(visited));

  while (not que.empty()) {
    Node node = que.front();
    que.pop();

    if (visited[node.v]) continue;
    visited[node.v] = true;

    if (node.v == end) {
      cout << node.dist - 1 << endl;
      return 0;
    }

    for (int i = 0; i < 16; ++i) {
      int v1 = node.v ^ (1 << i);

      if (exists[v1]) {
        que.push(Node(v1, node.dist + 1));
      }
    }
  }

  cout << -1 << endl;

  return 0;
}