def convert_keys(inverted_index):
    """Convert `str` words keys into `int` from inverted-index.

	Json convert doc id key in str, must convert in int.

	:param inverted_index: inverted_index to convert
	:tyep inverted_index: dict
	:return: converted inverted-index

	"""
    new_inverted_index = dict()
    for language in inverted_index:
        new_inverted_index[language] = dict()
        for first_letter in inverted_index[language]:
            new_inverted_index[language][first_letter] = dict()
            for two_letter in inverted_index[language][first_letter]:
                new_inverted_index[language][first_letter][two_letter] = dict()
                for word in inverted_index[language][first_letter][two_letter]:
                    new_inverted_index[language][first_letter][two_letter][word
                        ] = dict()
                    for doc_id in inverted_index[language][first_letter][
                        two_letter][word]:
                        new_inverted_index[language][first_letter][two_letter][
                            word][int(doc_id)] = inverted_index[language][
                            first_letter][two_letter][word][doc_id]
    return new_inverted_index
