program groupa;
var
 a:array [1..50] of longint;
 n,l,r,num1,num2,num3,num4:longint;
 f1,f2:text;

procedure init;
var i:longint;
begin
 assign(f1,'groupa.in'); reset(f1);
 assign(f2,'groupa.out'); rewrite(f2);
 readln(f1,n);
 for i:=1 to n do read(f1,a[i]);
 readln(f1);
 read(f1,l,r);
 close(f1);
 num1:=0;
 num2:=0;
 num3:=0;
 num4:=0;
 for i:=1 to n do begin
  if a[i]<l then num1:=num1+(l-a[i]);
  if a[i]>r then num2:=num2+(a[i]-r);
  if (a[i]>l)and(a[i]<=r) then num3:=num3+(a[i]-l);
  if (a[i]<r)and(a[i]>=l) then num4:=num4+(r-a[i]);
 end;
end;

procedure play;
var l,r,k:longint;
begin
 if (num1>num2+num3)or(num2>num1+num4) then writeln(f2,-1)
      else begin
       if num1=num2 then begin writeln(f2,num1);  end;
       if num1<num2 then begin writeln(f2,num2); end;
       if num1>num2 then begin writeln(f2,num1); end;
      end;
 close(f2);
end;

begin
 init;
 play;
end.