\documentclass{llncs}

\usepackage[english]{babel}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

% \usepackage{xcolor}
% \usepackage{tabu}
\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat=1.9}
\usetikzlibrary{shapes}
\usetikzlibrary{fit}

\usepackage{amsmath}
\usepackage{mathdots}
\usepackage{mathtools}
\mathtoolsset{showonlyrefs,showmanualtags}
\usepackage{mathrsfs}
\usepackage{csquotes}

\usepackage[pdftex]{hyperref}

\newcommand{\R}{\mathbb{R}}
\newcommand{\Oh}{\mathcal{O}}
\newcommand{\Ih}{\mathcal{I}}
\newcommand{\Ell}{\mathcal{L}}

\newcommand{\abs}[1]{\left\vert #1 \right\vert}
\newcommand{\powerset}[1]{\mathcal{P}\left( #1 \right)}
\newcommand{\setnot}[1]{\overline{#1}}
\newcommand{\setsymdiff}{\,\triangle\,}

\newcommand{\defeq}{\coloneqq} %Mathtools already defines this

\DeclareMathOperator{\st}{s.t.}