using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		
		
		Array.Sort(D);
		if(CheckZero()){
			Console.WriteLine(0);
			return;
		}
		if(CheckOne()){
			Console.WriteLine(1);
			return;
		}
		if(CheckTwo()){
			Console.WriteLine(2);
			return;
		}
		Console.WriteLine(-1);
		
	}
	
	bool CheckZero(){
		return X == 0 && Y == 0;
	}
	
	
	bool CheckOne(){
		for(int i=0;i<N;i++){
			if(X + Y == D[i]) return true;
		}
		return false;
	}
	
	bool CheckTwo(){
		bool ret = true;
		long[] TT = new long[]{X - Y, X + Y};
		for(int k=0;k<2;k++){
			long T = TT[k];
			bool chk = false;
			for(int i=0;i<N;i++){
				long r0 = D[i];
				if(T <= 2 * r0) {chk = true; break;}
				if(D[N-1] + r0 < T) continue;
				int l = i + 1;
				int r = N;
				if(D[l] + r0 >= T){
					if(D[l] - r0 <= T) {chk = true; break;}
					continue;
				}
				while(r - l > 1){
					int c = (r + l) / 2;
					if(D[c] + r0 < T){
						l = c;
					} else {
						r = c;
					}
				}
				if(r == N) continue;
				if(D[r] - r0 <= T) {chk = true; break;}
			}
			ret &= chk;
		}
		return ret;
	}
	
	
	
	
	
	
	
	int N;
	long[] D;
	long X,Y;
	public Sol(){
		N = ri();
		D = rla();
		var d = rla();
		X = d[0]; Y = d[1];
		if(X < 0) X *= -1;
		if(Y < 0) Y *= -1;
		if(Y > X) { Swap(ref X, ref Y);}
	}
	void Swap<T>(ref T x, ref T y){
		T tmp = x; x = y; y = tmp;
	}

	static String rs(){return Console.ReadLine();}
	static int ri(){return int.Parse(Console.ReadLine());}
	static long rl(){return long.Parse(Console.ReadLine());}
	static double rd(){return double.Parse(Console.ReadLine());}
	static String[] rsa(char sep=' '){return Console.ReadLine().Split(sep);}
	static int[] ria(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>int.Parse(e));}
	static long[] rla(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>long.Parse(e));}
	static double[] rda(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>double.Parse(e));}
}