有点复杂


str_1=input()
a = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
str_2=''
for i in str_1:
    if i in a:
        str_2 += i
    else:
        if str_2 != '':
            if str_2[-1] !=' ':
                str_2 += ' '
str_2 = str_2.split(' ')[::-1]
print(' '.join(i for i in str_2))