Find the maximum likelihood estimator of $\displaystyle \theta$ for the probability function $\displaystyle f(x,\theta)=\frac{e^-0.5(x-\theta)^2}{\sqrt2\pi}$

Since I am very poor at latex,here are something that have gone missing like

1.It is the square root of 2pi at the denominator not only the square root of 2

2.It is e to the power -(x-theta)/2.