\begin{tikzpicture}[scale = 0.5,]
    \draw[] (0,0)-- (1,1)--(2,0)--(3,1)--(4,2)-- (5,1)--(6,0)--(7,1)--(8,0);
    \filldraw [] (3,1) circle (2pt);
    \filldraw [] (5,1) circle (2pt);
    \draw[dashed] (0,0)--(8,0);
\end{tikzpicture}