求一个数的最大公约数

__author__ = 'JanGin_Chan'
"'get the largest factor for the given non-prime number'"
number = raw_input('please input a number:\n')
num = int(number)
factor = num / 2
while factor > 1:
    if num % factor == 0:
        print '%s is the largest factor of the %s' % (factor,num)
        break
    factor -= 1
else:
    print 'the largest factor of %s is itself' % number