In the sequence
\[..., a, b, c, d, 0, 1, 1, 2, 3, 5, 8,...\]
each term is the sum of the two terms to its left. Find $a$.
$\textbf{(A)}\ -3 \qquad\textbf{(B)}\ -1 \qquad\textbf{(C)}\ 0 \qquad\textbf{(D)}\ 1 \qquad\textbf{(E)}\ 3$
We work backwards to find $a$. 
\[d+0=1\implies d=1\]
\[c+1=0\implies c=-1\]
\[b+(-1)=1\implies b=2\]
\[a+2=-1\implies a=\boxed{\textbf{(A)}-3.}\]
--Solution by [TheMaskedMagician](https://artofproblemsolving.comhttp://www.artofproblemsolving.com/Forum/memberlist.php?mode=viewprofile&u=200685)