var
  n,up,down,i,j,total:longint;
  a:array[0..1000]of longint;

    procedure sort(l,r: longint);
      var
         i,j,x,y: longint;
      begin
         i:=l;
         j:=r;
         x:=a[(l+r) div 2];
         repeat
           while a[i]<x do
            inc(i);
           while x<a[j] do
            dec(j);
           if not(i>j) then
             begin
                y:=a[i];
                a[i]:=a[j];
                a[j]:=y;
                inc(i);
                j:=j-1;
             end;
         until i>j;
         if l<j then
           sort(l,j);
         if i<r then
           sort(i,r);
      end;

procedure init;
var
  i:longint;
  x:real;
begin
  assign(input,'groupa.in'); reset(input);
  assign(output,'groupa.out'); rewrite(output);
  readln(n);
  for i:=1 to n do read(a[i]);
  readln(down,up);
  for i:=1 to n do x:=x+a[i];
  x:=x/n;
  if (x<down)or(x>up) then
  begin
    writeln(-1);
    close(input);
    close(output);
    halt;
  end;
end;

function yes:boolean;
var
  i:longint;
begin
  for i:=1 to n do
  if (a[i]<down)or(a[i]>up) then exit(false);
  exit(true);
end;

begin
  init;
  repeat
    sort(1,n);
    for i:=1 to n do
    begin
      if a[i]<down then
      begin
        j:=n;
        while a[i]<down do
        begin
          dec(a[j]);
          inc(a[i]);
          if a[j]=down then dec(j);
          inc(total);
        end;
        break;
      end
      else if a[i]>up then
      begin
        j:=1;
        while a[i]>up do
        begin
          dec(a[i]);
          inc(a[j]);
          if a[j]=up then inc(j);
          inc(total);
        end;
        break;
      end;
    end;
  until yes;
  writeln(total);
  close(input);
  close(output);
end.