\documentclass[border=1pt]{standalone}
\usepackage[polish]{babel}
\usepackage[utf8]{inputenc} 
\usepackage[T1]{fontenc}
\usepackage{fourier}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}
\foreach \i/\j in {1/5,2/10,3/15,4/20,5/25,6/30,7/35,8/40,9/45,10/50} 
  \draw[fill=gray!\j] (\i,0) circle (0.4cm);
\end{tikzpicture}

\end{document}