import random

n = 10
flag_len = 20
state = [random.randint(0, (1 << n) - 1) for i in range(n)]
k = 0

def update_state():
    for i in range(n):
        state.append(state[0])
        for j in range(1, n):
            state[j] ^= ((state[0] >> j) & 1) << i
        state.pop(0)

def get_random():
    global k
    if(k == n):
        k = 0
        update_state()
    k += 1
    return state[k - 1]

flag='ctf{' + (''.join([chr(get_random() % 26 + ord('a')) for i in range(flag_len)])) + '}'
print(flag)
update_state()
print(state)