import itertools

def iter_cons(it):
    for x in it:
        for c in x:
            if c not in 'aeiou':
                yield c

def parelles_consonants1(it):
    itaux= iter_cons(it)
    x1 = next(itaux, '')
    for x in itaux:
        yield x1+x
        x1 = x
            
def parelles_consonants2(it):
    x1= 'a'
    for x in it:
        for x2 in x:
            if x1 not in 'aeiou' and x2 not in 'aeiou':
                yield x1+x2
                x1 = x2
            elif x1 in 'aeiou':
                x1 = x2

def parelles_consonants3(it):
    it2 = itertools.chain.from_iterable(it)
    it3 = filter(lambda c: c not in 'aeiou', it2)
    it4 = itertools.pairwise(it3)
    it5 = map(''.join, it4)
    return it5


parelles_consonants = parelles_consonants3