program Operatii;
var
   Fl : text;
   n, i, s, a, p_max : longint;
begin
   Assign(Fl,'operatii.in');
   Reset(Fl);
   ReadLn(Fl,n);
   s := 0;
   p_max := 0;
   for i := 1 to n do
      begin
         Read(Fl,a);
         if (a <> 0) and (a > p_max) then
            p_max := a;
         if (a = 0) or (i = n) then
            begin
               s := s + p_max;
               p_max := 0;
            end;
      end;
   Close(Fl);

   Assign(Fl,'operatii.out');
   ReWrite(Fl);
   Writeln(Fl,s);
   Close(Fl);
end.