#include<stdio.h>
int h(int a, int b)
{
	int cnt = 0;
	while (a > 0 || b > 0)
	{
		if (a % 2 != b % 2)
			cnt++;
		a /= 2;
		b /= 2;
	}
	return cnt;
}
int main()
{
	int n;
	scanf("%d", &n);
	int i, j;
	int a[1005];
	scanf("%d %d", &a[0], &a[n + 1]);
	for (i = 0; i < n; i++)
		scanf("%d", &a[i + 1]);
	n += 2;
	int dp[1005];
	for (i = 0; i < n; i++)
		dp[i] = -1;
	dp[0] = 0;
	int q[1005], l, r;
	q[0] = 0;
	l = 0;
	r = 1;
	while (l < r)
	{
		i = q[l];
		l++;
		for (j = 0; j < n; j++)
		{
			if (h(a[i], a[j]) < 2)
			{
				if (dp[j]<0 || dp[j]>dp[i] + 1)
				{
					dp[j] = dp[i] + 1;
					q[r] = j;
					r++;
				}
			}
		}
	}
	if (dp[n - 1] < 0)
		dp[n - 1]++;
	printf("%d\n", dp[n - 1] - 1);
	return 0;
}