import string
f = lambda s: (lambda f: ' '.join(f(w) for w in s.split()))(lambda w: (lambda f: f(f, 0, 1))(lambda f, i, j: (([c for c in w if c in string.ascii_letters][-j] + f(f, i+1, j+1) if w[i] in string.ascii_letters else w[i] + f(f, i + 1, j)) if i < len(w) else '')))
print(f('Hello world! My name is Ian')) # 'olleH dlrow! yM eman si naI.'