#include <bits/stdc++.h>
#define MOD 1000000007LL
using namespace std;
typedef long long ll;
typedef pair<int,int> P;

int n;
int d[100001];
int x,y;
vector<int> vi[2];

int main(void){
	scanf("%d",&n);
	for(int i=0;i<n;i++){
		scanf("%d",&d[i]);
		vi[d[i]%2].push_back(d[i]);
	}
	scanf("%d%d",&x,&y);
	if(x==0 && y==0){
		printf("0\n");
		return 0;
	}
	sort(d,d+n);
	sort(vi[0].begin(),vi[0].end());
	sort(vi[1].begin(),vi[1].end());
	for(int i=0;i<n;i++){
		if(d[i]==(abs(x)+abs(y))){
			printf("1\n");
			return 0;
		}
	}
	for(int i=0;i<n;i++){
		int rest=abs(x)+abs(y)-d[i];
		rest=abs(rest);
		if(vi[rest%2].size()==0)continue;
		int vo=lower_bound(vi[rest%2].begin(),vi[rest%2].end(),rest)-vi[rest%2].begin();
		if(vo!=vi[rest%2].size() && vi[rest%2][vo]==rest){
			printf("2\n");
			return 0;
		}
	}
	printf("-1\n");
	return 0;
}