Decimal digit selection pair (1, 8) (2,7) (3,6) (4,5)

Hundred-digit selection pair (1, 8) (2,7) (3,6) (4,5)

If the company selects (2,8), only (3,6) (4,5) can be selected for the hundred digits.

If the company chooses (3,7), only (100) (4,5) can be selected for 1 00 digits.

If a company chooses (4,6), one hundred out of ten can only choose (1, 8) (2,7).

Each number has two optional numbers, so you can get 2*2 different solutions by choosing three groups of numbers.

The total number of solutions is 3*2*4=24.