ans;
a[200000];
n,x,y;
c(int*a,int*b){return*a-*b;}
f(x){
	int l=0,r=n;
	while(r-l>1){
		int m=(l+r)/2;
		if(a[m]>x)r=m;
		else l=m;
	}
	return a[l]==x;
}
g(i){
	return f(x>a[i]?x-a[i]:a[i]-x);
}
main(){
	scanf("%d",&n);
	for(int i=0;i<n;i++)scanf("%d",a+i);
	qsort(a,n,4,c);
	scanf("%d%d",&x,&y);
	x=abs(x)+abs(y);
	if(f(x)){puts("1");return 0;}
	else{
		for(int i=0;i<n;i++)if(g(i)){puts("2");return 0;}
	}
	puts("-1");
}