There are 12 students. Compute the probability that at least 3 students are born in the same month.

Am I right with:

$\displaystyle {12 \choose 3} \times (\frac{1}{12})^3$

OR

$\displaystyle (\frac{1}{3} \times \frac{1}{12}) + (\frac{1}{3} \times \frac{1}{12}) + (\frac{1}{3} \times \frac{1}{12})$