belong to latex symbol code example
Example: latex x element of symbol
\documentclass{article}
\usepackage{graphicx}
\usepackage{amsmath}
\newcommand\Inn{%
\mathrel{\ooalign{$\subset$\cr\hfil\scalebox{0.8}[1]{$=$}\hfil\cr}}%
}
\begin{document}
\[
A\in B % one stroke in middle
\]
\[
A\Inn B % two strokes in middle
\]
\end{document}