Probability from a gamma law given its mean and variance

Let $X$ be a random variable with the probability density function

$$f(x|r,\lambda)=\frac{\lambda^r}{(r-1)!}x^{r-1}e^{-\lambda x},\quad x>0, \lambda>0, r>0.$$

If $E(X)=2$ and $\mathrm{Var}(X)=2$, then $P(X<1)$ equals __________________