import std.algorithm, std.conv, std.range, std.stdio, std.string;
import std.math;      // math functions

void main()
{
  auto n = readln.chomp.to!int;
  auto d = readln.split.to!(int[]);
  auto rd = readln.split.to!(int[]), x = rd[0].abs, y = rd[1].abs, d1 = x + y;

  auto ds = d.sort();

  if (ds.contains(d1)) {
    writeln(1);
    return;
  }

  auto o = ds.filter!"a&1".array;
  auto e = ds.filter!"a&0".array;

  if (d1&1) {
    if (!o.empty && !e.empty && o[$-1]+e[$-1] >= d1) {
      writeln(2);
      return;
    }
  } else {
    if (o.length >= 2 && o[$-1]+o[$-2] >= d1 || e.length >= 2 && e[$-1]+e[$-2] >= d1) {
      writeln(2);
      return;
    }
  }

  writeln(-1);
}