#回数是指从左向右读和从右向左读都是一样的数，例如12321，909

def get_back_num(s):

#得到中位数的下标

def getCenterPosition(s):

return int(len(s)/2)

def decide(l):

str=s[-l:][::-1]

if s[:l]==str:

return True

else:

return False

return decide(getCenterPosition(s))

print(get_back_num('12321'))