#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n;
    cin >> n;

    vector<int> d(n);
    for (int i = 0; i < n; i++) {
        cin >> d[i];
    }
    sort(d.begin(), d.end());

    int x, y;
    cin >> x >> y;
    int t = x + y; y = x - y; x = t;
    int z = max(abs(x), abs(y));

    int ans = -1;

    for (int i = 0; i < n - 1; i++) {
        if (d[i + 1] - d[i] <= z && z <= d[i] + d[i + 1]) ans = 2;
    }
    
    for (int i = 0; i < n; i++) {
        if (z == d[i]) ans = 1;
    }

    if (x == 0 && y == 0) ans = 0;

    cout << ans << endl;

    return 0;
}