#include <bits/stdc++.h>
using namespace std;

long long n, x, y, a, t, r=3;
int main() {
	scanf("%lld", &n);
	long long d[n];
	for (int i = 0; i < n; ++i) scanf("%lld", &d[i]);
	sort(d, d+n);
	scanf("%lld %lld", &x, &y);
	a = abs(x) + abs(y);
	if (a==0) {
		printf("0\n");
		return 0;
	}
	
	for (int i = 0; i < n; ++i) {
		if (d[i]==a) r = 1;
		else if (binary_search(d+i+1, d+n, abs(a-d[i])) || binary_search(d+i+1, d+n, a+d[i]))
			if (r==3) r = 2;
	}
	if (r==3) r = -1;
	printf("%lld\n", r);
}