12. In the "口" between the two rows of numbers below, choose four arithmetic operation symbols to fill in, so that the difference between the results of the two expressions (1) and (2) is as large as possible (the result is a positive integer). Then the maximum difference between the two expressions (1) and (2) is $\qquad$.
(1) 1口2口3口4口5口6口7=
(2) 7口6口5口4口3口2口1=
【Analysis】Analysis:
To make the difference large, one number should be small, and the other should be large
$$
\begin{array}{l}
\text { Small: } 1+2-3-4+5+6-7=0 \\
\text { Large: } 7 \times 6 \times 5 \times 4 \times 3 \times 2+1=5041 \\
5041-0=5041
\end{array}
$$