How to typeset Cyrillic characters in tikzpicture nodes?

[Blezz-tech]

This code not working:

\usepackage{tikz}
\usetikzlibrary{positioning}
\tikzstyle{center} = [align=center]

\begin{document}
    \begin{tikzpicture}[domain=0:4]
        %Nodes
        \node[center] (InfiniteFractions) {Бесконечные дроби};
        \node[center] (PeriodicFractions) [below left  = of InfiniteFractions] {
            Переодические: \\
            0,(6); 7,7(8) \\
            $\frac{22}{7}$; 6,(1)
        };
        \node[center] (NonPeriodicFractions) [below right = of InfiniteFractions] {
            Непериодические: \\
            $\pi \approx 3,1415926535$ \\
            $e \approx 2,71828182846$
        };
        %Lines
        \draw[->] (InfiniteFractions.south) -- (PeriodicFractions.north);
        \draw[->] (InfiniteFractions.south) -- (NonPeriodicFractions.north);
    \end{tikzpicture}
\end{document}

But if you remove the words with Cyrillic characters, then it works:

\usepackage{tikz}
\usetikzlibrary{positioning}
\tikzstyle{center} = [align=center]

\begin{document}
    \begin{tikzpicture}[domain=0:4]
        %Nodes
        \node[center] (InfiniteFractions) {InfiniteFractions};
        \node[center] (PeriodicFractions) [below left  = of InfiniteFractions] {
            PeriodicFractions: \\
            0,(6); 7,7(8) \\
            $\frac{22}{7}$; 6,(1)
        };
        \node[center] (NonPeriodicFractions) [below right = of InfiniteFractions] {
            NonPeriodicFractions: \\
            $\pi \approx 3,1415926535$ \\
            $e \approx 2,71828182846$
        };
        %Lines
        \draw[->] (InfiniteFractions.south) -- (PeriodicFractions.north);
        \draw[->] (InfiniteFractions.south) -- (NonPeriodicFractions.north);
    \end{tikzpicture}
\end{document}

I am not sure what could be the problem?