Question 19
N1 (UKR) Four integers are marked on a circle. At each step we simultaneously replace each number by the difference between this number and the next number on the circle, in a given direction (that is, the numbers $a,b,c,d$ are replaced by $a-b,b-c,c-d,d-a$). Is it possible after $1996$ such steps to have numbers $a,b,c,d$ such that the numbers $|bc-ad|,|ac-bd|,|ab-cd|$ are primes?