void main(){
  import std.stdio, std.string, std.conv, std.algorithm;
  import std.math, std.range;

  int n; rd(n);
  auto d=readln.split.to!(int[]);
  int x, y; rd(x, y);
  
  if(x==0 && y==0){writeln(0); return;}
  auto d0=x.abs+y.abs;
  if(count(d, d0)){writeln(1); return;}

  sort(d);
  auto p=assumeSorted(d);
  foreach(i; 0..n){
    if(p.canFind(d0-d[i])){writeln(2); return;}
    if(p.canFind(d0+d[i])){writeln(2); return;}
    if(p.canFind(d[i]-d0)){writeln(2); return;}
  }

  writeln(-1);
}

void rd(T...)(ref T x){
  import std.stdio, std.string, std.conv;
  auto l=readln.split;
  assert(l.length==x.length);
  foreach(i, ref e; x){
    e=l[i].to!(typeof(e));
  }
}