#include <stdio.h>
#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

int main(){
	
	int N;
	cin>>N;
	
	int s,e;
	N += 2;
	cin>>s>>e;
	
	vector<int> x(N);
	x[0] = s;
	x.back() = e;
	
	rep(i,N-2){
		cin>>x[i+1];
	}
	
	map<int,int> mp;
	rep(i,N){
		mp[x[i]] = i;
	}
	
	vector<int> dis(N,Inf);
	dis[0] = 0;
	queue<int> Q;
	Q.push(0);
	
	while(Q.size()>0){
		int u = Q.front();
		Q.pop();
		
		rep(i,30){
			int v = x[u] ^ (1<<i);
			if(!mp.count(v))continue;
			int ind = mp[v];
			if(dis[ind]!=Inf)continue;
			Q.push(ind);
			dis[ind] = dis[u]+1;
		}
	}
	
	int ans = dis.back();
	
	if(ans==Inf)ans = -1;
	else ans--;
	
	cout<<ans<<endl;
	
    return 0;
}