#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
#include <iterator>
using namespace std;

int solve(const vector<int>& v, long long dist)
{
    if(dist == 0)
        return 0;
    if(find(v.begin(), v.end(), dist) != v.end())
        return 1;

    vector<vector<int> > v2(2);
    for(int a : v)
        v2[a%2].push_back(a);
    for(int i=0; i<2; ++i)
        sort(v2[i].begin(), v2[i].end());

    for(int i=0; i<2; ++i){
        int j = (dist - i) % 2;
        int n = v2[j].size();
        if(n == 0)
            continue;

        int k = 0;
        for(int a : v2[i]){
            while(k < n-1 && v2[j][k+1] <= a + dist)
                ++ k;
            int b = v2[j][k];
            if(dist <= a + b && abs(a - b) <= dist)
                return 2;
        }
    }
    return -1;
}

int main()
{
    int n;
    cin >> n;
    vector<int> v(n);
    for(int i=0; i<n; ++i)
        cin >> v[i];

    int x, y;
    cin >> x >> y;
    int dist = abs(x) + abs(y);

    cout << solve(v, dist) << endl;

    return 0;
}