\begin{tikzpicture}

\foreach[count=\xi] \len in {1,3,2,5,4,2,1} {
	\draw[|-|] (0, -\xi/2)  node [left] {\alphalph{\xi}}  -- node [above] {$\len$} (\len, -\xi/2);
}

\begin{scope}[yshift=-2cm, xshift=7cm]
\draw[|-] (0,  0) -- node [below] {a} (1, 0);
\draw[|-] (1,  0) -- node [below] {f} (3, 0);
\draw[|-|] (3, 0) -- node [below] {b} (6, 0);
\end{scope}

\end{tikzpicture}