def binary_search(List, string, lo = 0):
    hi = len(List)
    while lo < hi:
        mid = (lo+hi)//2
        midval = List[mid]
        if midval < string:
            lo = mid+1
        elif midval > string:
            hi = mid
        else:
            return True
    return False

def interlocked():
    List = wordlist()
    for word in List:
        word1 = ''
        word2 = ''
        for letter in word:
            if word.index(letter) % 2 == 0:
                word1 = word1 + letter
            else:
                word2 = word2 + letter
        if binary_search(List, word1) and binary_search(List, word2):
            print(word1, word2)