单点时限: 1.0 sec
内存限制: 256 MB
Compute and output approximate value of $e$ with %.6f format using formula:
%.6f
$$e = 1+\frac{1}{1!}+\frac{1}{2!}+\frac{1}{3!}+\cdots$$
until the last item is less than $10^{-6}$.