Write a program to find values of a and M, with M as small as possible, such that the hash function (a * k) % M for transforming the kth letter of the alphabet into a table index produces distinct values (no collisions) for the keys S E A R C H X M P L. The result is known as a perfect hash function.

I found this answer on Chegg, but it is wrong since we have to find the values of m and a but in this code, he gets a=3 and m=20!!!