Confidence coefficient of an interval based on the sample minimum

Let $X_1,…,X_n$ be a random sample from a population with density

$$f(x,\mu)=\begin{cases}e^{\mu-x}, & x>\mu,\ 0, & \text{otherwise,}\end{cases}$$

and let $X_{(1)}=\min\{X_1,X_2,…,X_n\}$. Then $\left(X_{(1)}-\frac2n\log_e5, X_{(1)}\right)$ is a ____________% confidence interval for $\mu$.