\begin{tikzpicture}[scale = 0.45]
    \draw (0,6) -- (9.5,0);
    \draw [ultra thick] (0,0)--(7,0)--(7,1)--(6,1)--(6,2)--(4,2)--(4,3)--(3,3)--(3,4)--(1,4)--(1,5)--(0,5)--cycle;
    \draw [red, ultra thick, fill = green!30](0,0)--(5,0)--(5,2)--(3,2)--(3,3)--(2,3)--(2,4)--(0,4)--cycle;
    \draw[fill = yellow!30] (1,0) rectangle (2,1);
    \draw[fill = yellow!30] (4,0) rectangle (5,1);
    \draw[step=1cm,gray,very thin] (0,0) grid (10,6);
\end{tikzpicture}