#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <map>
#include <vector>
#include <algorithm>
#include <iostream>

using namespace std;
#define PRINT(x) { std::cout << #x << ": " << x << std::endl; }
//#define PRINT(x)

int main(int argc, char *argv[])
{
    int n;
    scanf("%d", &n);
    vector<int> d(n);
    for (int i = 0; i < n; ++i)
    {
        scanf("%d", &d[i]);
    }
    int x, y;
    scanf("%d %d", &x, &y);
    if (x == 0 && y == 0)
    {
        puts("0");
        return 0;
    }

    int D = abs(x) + abs(y);
    vector<int>::iterator it = find(d.begin(),
                                    d.end(),
                                    D);
    if (it != d.end())
    {
        puts("1");
        return 0;
    }

    bool ok = false;
    for (int i = 0; i < n; ++i)
    {
        int dmin, dmax;
        if (D - d[i] > 0)
        {
            dmin = D - d[i];
            dmax = dmin + 2 * d[i];
        }
        else
        {
            dmin = d[i] - D;
            dmax = dmin + 2 * D;
        }
        for (int j = i; j < n; ++j)
        {
            int dd = d[j] - dmin;
            if (dd < 0) continue;
            if (dd % 2 == 1) continue;
            if (dmax - d[j] < 0) continue;
            ok = true;
            i = n;
            break;
        }
    }
    if (ok)
    {
        puts("2");
    }
    else
    {
        puts("-1");
    }
    return 0;
}