I want to create a rectangle Box with three intersected circles:
\documentclass[a4paper,11pt,fleqn]{scrartcl}
\usepackage{pgf,tikz}
\usetikzlibrary{arrows,shadows,decorations.pathreplacing,intersections,positioning,fit,calc,backgrounds}
\def\firstcircle{(0,0) circle (1.5cm)}
\def\secondcircle{(60:2.1cm) circle (1.5cm)}
\def\thirdcircle{(0:2.1cm) circle (1.5cm)}
\begin{document}
\begin{figure}[H]
\centering
\begin{tikzpicture}
\begin{scope}
\clip \firstcircle;
\clip \secondcircle;
\fill[red] \thirdcircle;
\end{scope}
\node (firstcircle) {};
\node (secondcircle) {};
\node (thirdcircle) {};
\draw[name=first] \firstcircle node[below] (A) {$A$};
\draw[name=second] \secondcircle node [above] (B) {$B$};
\draw[name=third] \thirdcircle node [below] (C) {$C$};
\node (box) [fit=(firstcircle)(secondcircle)(thirdcircle), inner sep=1cm,draw,rounded corners] {};
\end{tikzpicture}
\end{figure}
\end{document}
My Problem is: The rectangle should go around all cirles.


! LaTeX Error: Unknown float option 'H'.and it isn't clear how you want to change the output, which has intersecting circles already. – David Carlisle Apr 17 '17 at 11:21(firstcircle),(secondcircle)etc are just nodes of minimum size at the origin. Add some text to them and you'll see it. You have to make nodes with circle shape to make thefitthing work. – Rmano Apr 17 '17 at 11:48