def encode_list(list1):
    from itertools import groupby
    
    return [[len(list(group)), key] for key, group in groupby(list1)]
def is_not_prime(n):
    import math
    
    result = False
    for i in range(2,int(math.sqrt(n)) + 1):
        if n % i == 0:
            result = True
    return result