jmc

We know that $a+bi+c+di+e+fi=2i$. Thus, the real parts add up to 0 and the imaginary parts add up to 2. We then have $$\begin{array}{rl}a+c+e& =0\\ b+d+f& =2\end{array}$$ We know that $b=3$, therefore $d+f=\boxed{-1}$