class Primes:
    def __init__(self, maximum):
        sieve = [i for i in range(maximum+1)]
        sieve[1] = 0
        i = 2
        while i * i <= maximum:
            if sieve[i] != 0:
                for j in range(i*2, maximum+1, i):
                    sieve[j] = 0
            i += 1

        current_list = [3]
        sieve[0] = [None]
        sieve[1] = [None]
        for i in range(3, len(sieve)):
            if sieve[i] == 0:
                sieve[i] = current_list
            else:
                current_list = [i]

        last_prime = None
        for i in range(len(sieve)-1, -1, -1):
            if sieve[i] == i:
                last_prime = i
            elif len(sieve[i]) == 1:
                sieve[i].append(last_prime)
        self._data = sieve

    def print(self):
        for i, v in enumerate(self._data):
            print(i, v)

def main():
    s = Primes(100)
    s.print()