PLEASE WRITE IN FORTRAN 90 LANGUAGE, THANKS!

The greatest common divisor (GCD) of two integers a and b is the largest positive integer that divides both a and b The Euclidean algorithm for finding GCD(a, b) is as follows: if b O, GCD(a, b)-a. Otherwise, let a = bq + r, where q is quotient and r is the remainder. Then GCD(a, b) = GCD(b, Write an external function subprogram to calculate the GCD of two integers. First, solve using a non-recursive algorithm and then by a recursive algorithm