#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef int _loop_int;
#define REP(i,n) for(_loop_int i=0;i<(_loop_int)(n);++i)
#define FOR(i,a,b) for(_loop_int i=(_loop_int)(a);i<(_loop_int)(b);++i)
#define FORR(i,a,b) for(_loop_int i=(_loop_int)(b)-1;i>=(_loop_int)(a);--i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define CHMIN(a,b) a=min((a),(b))
#define CHMAX(a,b) a=max((a),(b))

// mod
const ll MOD = 1000000007ll;
#define FIX(a) ((a)%MOD+MOD)%MOD

// floating
typedef double Real;
const Real EPS = 1e-11;
#define EQ0(x) (abs(x)<EPS)
#define EQ(a,b) (abs(a-b)<EPS)
typedef complex<Real> P;

int n;
int d[125252];
int ne, no;
int deven[125252], dodd[125252];
int x,y;

int main(){
  scanf("%d",&n);
  REP(i,n)scanf("%d",d+i);
  scanf("%d%d",&x,&y);
  x = abs(x);
  y = abs(y);
  if(x==0 && y==0){
    puts("0");
    return 0;
  }
  // check once
  int dist = x+y;
  REP(i,n)if(dist == d[i]){
    puts("1");
    return 0;
  }
  // check double
  sort(d,d+n);
  ne = 0;
  no = 0;
  REP(i,n){
    if(d[i]%2==0){
      deven[ne++] = d[i];
    }else{
      dodd[no++] = d[i];
    }
  }
  const int INF = 1252183025;
  deven[ne] = dodd[no] = INF;
  REP(i,n){
    int s = d[i];
    int t;
    if((x+y)%2==s%2){
      // even
      t = *lower_bound(deven, deven+ne, -x-y+s);
    }else{
      // odd
      t = *lower_bound(dodd, dodd+no, -x-y+s);
    }
    if(t != INF && t <= s){
      puts("2");
      return 0;
    }
  }
  puts("-1");
  return 0;
}