2. Use the four digits 1, 2, 3, 4 to form a four-digit number $\overline{a b c d}$, with the following requirements:
(1) $a$, $b$, $c$, $d$ are all different; (2) $b$ is greater than both $a$ and $d$, and $c$ is also greater than both $a$ and $d$. How many such four-digit numbers are there? $\qquad$
【Analysis】 $b 、 c=3$ or $4, a 、 d=1$ or 2 , if $a=1, d=2$, we have 1342 or 1432. If $a=2, d=1$, we have 2341 or 2431. In total, there are 4.