Write a C function f that

• accepts, as input, two unsigned long ints, M and N
  • assume that both M and N are greater than zero
• yields, as its output, the greatest positive integer that divides both M and N
  • "divides" means divides evenly, with no remainder (i.e., zero remainder)
• has the prototype
  • unsigned long int f ( unsigned long int M, unsigned long int N ) ;