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

int main()
{
    int N;
    int D[100005];
    int distance;
    int ans = 3;
    cin >> N;
    for(int i = 0; i < N; i++) cin >> D[i];
    sort(D, D + N);
    { int a, b; cin >> a >> b; distance = abs(a) + abs(b); }
    int j = N - 1, k = 0;
    for(int i = 0; i < N; i++) {
        if(D[i] == distance) ans = min(ans, 1); 
        while(j > 0 && D[i] + D[j] > distance) j--;
        while(k < N - 1 && D[i] - D[k] > distance) k++;
        if(D[i] + D[j] == distance) ans = min(ans, 2);
        if(D[i] - D[k] == distance) ans = min(ans, 2);
    }
    if(distance == 0) cout << 0 << endl;
    else if(ans == 3) cout << -1 << endl;
    else cout << ans << endl;

    return (0);
}