from copy import deepcopy
from itertools import islice


def primes(n):
    """ Nice way to calculate primes.  Should be fast. """
    l = range(2, n + 1)
    _l = []
    while True:
        p = l[0]
        if p * p > n:
            return _l + l
        l = [i for i in l if i % p != 0]
        _l.append(p)


def calculate_decimal_places(numerator, denominator):
    numerator = (numerator - (numerator / denominator) * denominator) * 10
    digits = []
    while True:
        digit = numerator / denominator
        numerator = (numerator - digit * denominator) * 10
        digits.append(digit)
        if digits[-3:] == [0, 0, 0]:
            raise StopIteration
        yield digit


def has_cycle(decimal_places, n):
    d = decimal_places
    return list(islice(d, 0, n)) == list(islice(d, 0, n)) and \
           list(islice(d, 0, n)) == list(islice(d, 0, n))


def f_025_1():
    """ Second try.  I realized that only primes must be
    checked.  Therefore, my brute force approach worked. """
    l = []
    for d in primes(1000):
        for i in range(5, 10000):
            decimal_places = calculate_decimal_places(1, d)
            if has_cycle(decimal_places, i):
                l.append((i, d))
                break
    print(max(l))


def calculate_cycle(numerator, denominator):
    numerator = (numerator - (numerator / denominator) * denominator) * 10
    remainders = set([])
    while True:
        digit = numerator / denominator
        remainder = (numerator - digit * denominator)
        if remainder in remainders:
            raise StopIteration
        remainders.add(remainder)
        numerator = remainder * 10
        yield digit


def f_025_2():
    """ Understood trick with remembering remainder... """
    s = [(len(list(calculate_cycle(1, d))), d)
         for d in range(1, 1001)]
    print(max(s))


def f_025_3():
    """ Only testing primes... """
    s = [(len(list(calculate_cycle(1, d))), d)
         for d in primes(10000)]
    print(max(s))


f_025_3()


#print([(find_cycle_count(calculate_decimal_places(1, d)), d)
#       for d in range(1, 100)])

#print(find_cycle_count(calculate_decimal_places(22, 7)))

#l = []
#for d in range(1, 1000):
#    for i in range(5, 1000):
#        decimal_places = calculate_decimal_places(1, d)
#        if has_cycle_one_off(decimal_places, i):
#            l.append((i, d))
#            break
#        decimal_places = calculate_decimal_places(1, d)
#        if has_cycle(decimal_places, i):
#            l.append((i, d))
#            break

#def find_cycle_count(decimal_places):
#    cycles = []
#    for digit in decimal_places:
#        new_cycles = []
#        for cycle in cycles:
#            digits, length = cycle
#            if digits[0] == digit:
#                if len(digits[1:]) == 0:
#                    return length
#                new_cycles.append((digits[1:], length))
#            new_cycles.append((digits + [digit], length + 1))
#        new_cycles.append(([digit], 1))
#        cycles = new_cycles