Python-сообщество

from functools import reduce
 
print((lambda n : (lambda R: (lambda ns : (R(lambda self, x, xs, o, ts :
                              x and (lambda nxs : nxs + 
                                     (lambda nn, nh : reduce(lambda res, n : res*10 + n,
                                                             [nh] + [9]*nn,
                                                             0))
                                       (*divmod(ns(xs) - ns(nxs) + ts + x, 9)))
                                      ((xs+1)*o*10) or self(xs, o*10, ts+x)))
                              (n, 1, 0))
                   (R(lambda self, x, xs: xs and x + self(xs) or x)))
       (lambda f : (lambda hR : hR(hR))
                   (lambda r : lambda d, *a : f(r(r), *(tuple(reversed(divmod(d, 10))) + a)))))
      (int(input('your number?? '))))

N = 1239560
s = [0]+list( map(int, str(N)))
ind = len(s) - 1
for adder in (-1, 1):
    while 2*s[ind] == 9*(adder+1): ind -= 1
    s[ind] += adder
    ind += adder
    
s = s[:ind] + sorted(s[ind:])
M = int(''.join( map(str,s)))
print( N, '->', M )

from functools import reduce
R = lambda f : (lambda hR : hR(hR))(lambda r : lambda d, *a : f(r(r), *(tuple(reversed(divmod(d, 10))) + a)))
ns = R(lambda self, x, xs: xs and x + self(xs) or x)
fast_next = lambda n : (R(lambda self, x, xs, o, ts :
                          x and (lambda nxs : nxs + (lambda nn, nh : reduce(lambda res, n : res*10 + n,
                                                                     [nh] + [9]*nn,
                                                                     0))
                          (*divmod(ns(xs) - ns(nxs) + ts + x, 9)))
                         ((xs+1)*o*10) or  self(xs, o*10, ts+x)))(n, 1, 0)
 
def slow_next(n):
    ns = lambda n : sum(map(int, str(n)))
    nsum = ns(n)
    n+=1
    while ns(n) != nsum:
        n+=1
    return n
 
def isem_next(N):
    s = [0]+list( map(int, str(N)))
    ind = len(s) - 1
    for adder in (-1, 1):
        while 2*s[ind] == 9*(adder+1): ind -= 1
        s[ind] += adder
        ind += adder
    s = s[:ind] + sorted(s[ind:])
    M = int(''.join( map(str,s)))
    return M
 
for n in range(1,100000):
    by_slow, by_fast, by_isem = slow_next(n), fast_next(n), isem_next(n)
    assert by_slow == by_fast == by_isem, 'FAIL at {}: {},{},{} '.format(n, by_slow, by_fast, by_isem)