Error in a math expression

Question

I have a problem with this expression:

$$n \geq \Bigg\lvert \bigcup_{l \leq |A_{i}| \leq 2l} |A_{i}| \Bigg\rvert \geq \sum_{i = 1}^{N_{l}}\Bigg\lvert A_{i} \Biggl \bigcup_{j =1}^{i-1} A_{j}\Biggr \Bigg\rvert$$

The report is:

`* Local config file bblopts.cfg used * ("C:\Program Files\MiKTeX 2.9\tex\latex\00miktex\bblopts.cfg") ("C:\Program Files\MiKTeX 2.9\tex\generic\babel\italian.ldf" ("C:\Program Files\MiKTeX 2.9\tex\generic\babel\babel.def"))) (C:\Users\Stefano1\Desktop\Seminario\Seminario.aux) ("C:\Program Files\MiKTeX 2.9\tex\latex\amsfonts\umsa.fd") ("C:\Program Files\MiKTeX 2.9\tex\latex\amsfonts\umsb.fd") ("C:\Program Files\MiKTeX 2.9\tex\latex\base\omscmr.fd") [1{C:/ProgramData/MiKT eX/2.9/pdftex/config/pdftex.map}] [2] [3] [4] [5] [6] [7] [8] [9] ! Missing delimiter (. inserted). \bigcup@ l.296 ...}^{N_{l}}\Bigg\lvert A_{i} \Biggl \bigcup {j =1}^{i-1} A{j}\Biggr ...

? `

I don't understand where is the error.

Answer 1

Both after one \Biggl and one \Biggr a delimiter, such as \lvert or \rvert or any other (parenthessis, brace, dot), is missing. There's just a blank and another command following.

Compilable example code:

\documentclass{article}
\usepackage{amsmath,amssymb}
\begin{document}
\[
  n \geq \Bigg\lvert \bigcup_{l \leq |A_{i}| \leq 2l} |A_{i}|
  \Bigg\rvert \geq \sum_{i = 1}^{N_{l}}\Bigg\lvert A_{i} \Biggl\lvert
  \bigcup_{j =1}^{i-1} A_{j}\Biggr\rvert \Bigg\rvert
\]
\end{document}