documentclass[border=3mm]{standalone}

usepackage{tikz}


begin{document}

begin{tikzpicture}[xscale=1.2,font=footnotesize]
draw (0,0) -- (12,0);
%
foreachm/n in {0/1,3/N,4/N+1,7/2N,8/2N+1,11/3N}
    {node[scale=.7] at (m,0) {$|$};
     node[below,yshift=-5pt] at (m,0) {$n$};}
%
path
    node[above] at (1.5,0) {$B_1$}
    node[above] at (5.5,0) {$B_2$}
    node[above] at (9.5,0) {$B_3$};
end{tikzpicture}

end{document}