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(){
		
		long[] TT = new long[]{X - Y, X + Y};
		if(TT.Max() <= 2 * D[N-1]) return true;
		
		for(int i=0;i<N-1;i++){
			long r0 = D[i];
			
			if(D[i+1] - r0 > TT[0]) continue;
			if(D[N-1] + r0 < TT[0]) continue;
			
			int l,r,ll,rr;
			
			l = i + 1;
			r = N;
			
			while(r - l > 1){
				int c = (r + l) / 2;
				if(D[c] - r0 <= TT[0]){
					l = c;
				} else {
					r = c;
				}
			}
			
			ll = l;
			
			l = i + 1;
			r = N;
			
			while(r - l > 1){
				int c = (r + l) / 2;
				if(D[c] + r0 < TT[0]){
					l = c;
				} else {
					r = c;
				}
			}
			
			rr = r;
			
			if(D[ll] - r0 <= TT[1] && TT[1] <= D[rr] + r0) return true;
			
		}
		
		return false;
	}
	
	
	
	
	
	
	
	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));}
}