/* Form the n-th Fibonacci number, n > 1.    12 March 2022 */
Fib: procedure (n) returns (fixed binary (31));
   declare (i, n, f1, f2, f3) fixed binary (31);

   f1 = 0; f2 = 1;
   do i = 1 to n-2;
      f3 = f1 + f2;
      f1 = f2;
      f2 = f3;
   end;
   return (f3);

end Fib;