def return_kmers(input_string, k, index_from_beginning):
	"""
    Returns kmers from given input string.
    Length of returned kmers is k.
    :param input_string: str (string in which you want to find kmers)
    :param k: int (length of kmers you want to extract from your string)
    :param index_from_beginning: int (index from which input_string starts in original string)
    :return: list [(str, int), (str, int) ...] where str is kmer and int is its position in string
    """
	kmers = []
	i = 0
	while True:
		kmer = input_string[i:i + k]  # slicing kmer out of input string
		# print(kmer)
		if len(kmer) < k:  # if window is coming to the end
			break  # break
		kmers.append((kmer, index_from_beginning + i))  # appending kmer and its index in original string
		i += 1
	return kmers