This so complex product includes all the factors of the type (m - letter of the alphabet)
So, in the middle you will find ...(m- k)(m - l) (m -m ) (m -n) ... wait.. (m - m)! that is ... zero.
So the total product will be zero, and you do not have to make any algebra.
Answer: 0 because one factor is (m - m) which is 0.
