#pragma GCC optimize("O3")
#pragma GCC target("avx2")
#pragma GCC optimize("unroll-loops")
//#pragma GCC optimize ("Ofast")
#include <cstdio>
#include <vector>
#include <unordered_map>
#include <queue>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define FOR(i, m, n) for (int i = (m); i < (n); ++i)
#define rrep(i, n) for (int i = (n)-1; i >= 0; --i)
#define rfor(i, m, n) for (int i = (m); i >= (n); --i)
using ll = long long;

#ifdef _WIN32
#define getchar_unlocked _getchar_nolock
#define putchar_unlocked _putchar_nolock
#define fwrite_unlocked _fwrite_nolock
#define fread_unlocked _fread_nolock
#endif
#if __has_include(<library/dump.hpp>)
#include <library/dump.hpp>
#else
#define dump(...) ((void)0)
#endif

// #define USE_FREAD
#ifdef USE_FREAD
struct Input {
	static constexpr size_t MAX_SIZE = 4400019;
	char buf[MAX_SIZE];
	size_t i, end;
	Input() {
		i = 0;
		end = fread_unlocked(buf, 1, MAX_SIZE, stdin);
	}
	inline int gc() {
		if (i < end) {
			return buf[i++];
		} else {
			return EOF;
		}
	}
} in;
#define gc in.gc
#else
#define gc getchar_unlocked
#endif  // USE_FREAD

// #define USE_FWRITE
#ifdef USE_FWRITE
struct Output {
	static constexpr size_t MAX_SIZE = 4000009;
	char buf[MAX_SIZE];
	size_t i = 0;
	void pc(int c) {
		buf[i++] = c;
	}
	~Output() {
		fwrite_unlocked(buf, 1, i, stdout);
	}
} out;
#define pc out.pc
#else
#define pc putchar_unlocked
#endif  // USE_FWRITE

inline void inui(int& v) noexcept {
	v = 0;
	for (char c = gc(); '0' <= c && c <= '9'; c = gc()) v = v * 10 + (c - '0');
}
inline void inul(ll& v) noexcept {
	v = 0;
	for (char c = gc(); '0' <= c && c <= '9'; c = gc()) v = v * 10 + (c - '0');
}
inline void puti(int v) noexcept {
	if (v < 0) pc('-'), v = -v;
	char b[10];
	int n = 0;
	while (v) b[n++] = '0' + v % 10, v /= 10;
	if (!n) b[n++] = '0';
	while (n--) pc(b[n]);
}
inline void putui(int v) noexcept {
	char b[10];
	int n = 0;
	while (v) b[n++] = '0' + v % 10, v /= 10;
	if (!n) b[n++] = '0';
	while (n--) pc(b[n]);
}

// ---------------------------------------------------------------- //

int n, s, e, stone[500003], dist[500003];

int main() {
	inui(n), inui(s), inui(e);
	rep(i, n) inui(stone[i]);
	stone[n] = s;
	stone[n + 1] = e;

	unordered_map<int, int> hash(n + 2);
	rep(i, n) hash[stone[i]] = i;
	hash[s] = n;
	hash[e] = n + 1;

	queue<int> que;
	que.push(n);
	dist[n] = 1;
	while (!que.empty()) {
		int i = que.front();
		que.pop();
		int d = dist[i];
		if (i == n + 1) {
			putui(d - 2), pc('\n');
			return 0;
		}
		for (int bit = 1, _ = 30; _--; bit <<= 1) {
			if (auto it = hash.find(stone[i] ^ bit); it != hash.end()) {
				int j = it->second;
				if (dist[j] == 0) {
					dist[j] = d + 1;
					que.push(j);
				}
			}
		}
	}
	pc('-'), pc('1'), pc('\n');
}