\def\Longleftrightarrow{\Leftarrow\kern-12.5mu\Rightarrow}
\def\iff{\Leftarrow\kern-12.5mu\Rightarrow}
\def\doteq{\stackrel{\cdot}{=}}
\def\Longleftrightarrow{\Leftarrow\kern-12.5mu\Rightarrow}
\def\iff{\Leftarrow\kern-12.5mu\Rightarrow}
\def\doteq{\stackrel{\cdot}{=}}