$4\mathrm{.}17$ LAB: Draw square with diagonal

Write a program that inputs a side length for a square, and three characters. It outputs a square with the following pattern:

character $1$ before$/$below the diagonal

character $2$ on the diagonal

character $3$ above$/$after the diagonal

Each line ends with a blank space.

Ex: If the input is:

$5+$&$-$

the output is:

$$

&$---$

$+$&$---$

$++$&$--$

$+++$&$-$

$++++$&