import time
start=time.clock()
def func315(str):
list1=list(str)
list2=['a']*len(list1)
for i in range(len(list1)):
if list1[i].isalpha():
list2[len(list1)-i-1]=list1[i]
else:
list2[i] = list1[i]
return ''.join(list2)
print(func315('ab-cd'))
end=time.clock()
print('running time ={}ms'.format((end-start)*1000))