# vim: set fileencoding=utf8 :
def permu(xs):
    if xs:
        r , h = [],[]
        for x in xs:
            if x not in h:
                ts = xs[:]; ts.remove(x)
                for p in permu(ts):
                    r.append([x]+p)
            h.append(x)
        return r
    else:
        return [[]]

def permu2(xs):
    if len(xs)<2: yield xs
    else:
        h = []
        for x in xs:
            h.append(x)
            if x in h[:-1]: continue
            ts = xs[:]; ts.remove(x)
            for ps in permu2(ts):
                yield [x]+ps


#print permu(['a','a','c'])
#for i in permu2(['a','a','c']): print i
#for i in permu2(list(u"бер")): print ''.join(i)