program Programs;
var
  inp:Text;
  count,number,sum:int64;
begin
  Assign(inp,'input.txt');
  reset(inp);
  sum:=0;
  count:=0;
  number:=0;
  while (sum <= 10) and (not EOF(input)) do begin
      Read(inp,number);
      sum += number;
      inc(count);
  end;
  close(inp);
  Assign(inp,'output.txt');
  rewrite(inp);
  if sum > 10 then
    Write(inp,count)
  else
    Write(inp,-1);
  close(inp);
end.