program gls;
var
ss:array[1..50]of int64;{ke neng yao gai}

a,b,c,k,n,he,head,tail,p:longint;
f,g:text;
     procedure Sort(l, r: longint);
 var
  i, j, x, y: longint;
 begin
  i := l; j := r; x := ss[(l+r) DIV 2];
  repeat
    while ss[i] < x do i := i + 1;
    while x < ss[j] do j := j - 1;
    if i <= j then
    begin
      y := ss[i]; ss[i] := ss[j]; ss[j] := y;
      i := i + 1; j := j - 1;
    end;
  until i > j;
  if l < j then Sort(l, j);
  if i < r then Sort(i, r);
 end;
  function success:boolean;
  var flag:boolean;k:longint;
  begin    flag:=true;
      for k:=1 to n do
      if (ss[k]<a)or(ss[k]>b)
         then flag:=false;

    success:=flag;


  end;

begin
assign(f,'groupa.in');
reset(f);
assign(g,'groupa.out');
rewrite(g);
readln(f,n);
for k:=1 to n do
begin read(f,ss[k]);
      he:=he+ss[k];
end;
readln(f,a,b);

 sort(1,n);
 head:=1;
 if ss[n]>b then begin
 for k:=1 to n do if ss[k]>b then
   begin tail:=k;
     break;
   end; end else for k:=1 to n do
       begin  if ss[k]>a then
               begin tail:=k;
                     break;
                end;
       end;


 if ((he/n>b) or (he/n<a)) then write(g,'-1') else
  begin
   repeat begin if ss[head]<b then
                 begin

                       repeat begin
                         if ss[head]+1>b then head:=1;
                              dec(ss[tail]);
                              inc(ss[head]);
                              inc(p);
                       if head+1<=n then if ss[head]=a then inc(head);
                       if tail+1<=n then if ss[tail]=b then inc(tail);
                        end;until ((ss[head]=a)or(ss[head]=b))and(ss[tail]<=b);

                 end;


          end;
          until success;
   writeln(g,p);
  end;







close(g);close(f);
end.