import java.util.*;
public class Main{
public static void main(String[]args)
{
Scanner sc=new Scanner(System.in);
int n=sc.nextInt();
if(n<=0)
{
System.out.println("Invalid input");
return;
}

int[]arr=new int[n];
for(int i=0;i<n;i++)
{
arr[i]=sc.nextInt();
if(arr[i]<0)
{
System.out.println("Invalid input");
return;
}
}
int num=sc.nextInt();
int diff=sc.nextInt();
if(diff<0)
{
    System.out.println("Invalid input");
    return;
}
int difference=num-diff;
System.out.println(diff);
int count=0;
if(difference>0)
{
    
for(int i=0;i<n;i++)
{
if(arr[i]==num)
{
    if(arr[i]>=difference &&arr[i]<=target)
    {
   count++;
 
    }
}

}

}
else{
    System.out.println("-1");
}

}
}