def gcdIter(a, b):
    '''
    a, b: positive integers

    returns: a positive integer, the greatest common divisor of a & b.
    '''
    # Your code here

    global x
    global y
    if a>=b:

        x=a
        y=b
    else:
        x=b
        y=a
    if x%y==0:
        return y

    else:

        while x%y>=0 or y%y>=0:
            y=y-1

            if a%y==0 and b%y==0:

                return y