

def solve():

    key = [-1] * 21

    key[0] = ord('o')
    key[1] = ord('_')
    key[2] = ord('O')
    key[3] = ord(' ')
    key[15] = ord(' ')

    foo = bytearray(b'\x08\xed\x6c\x63\x72\x90\xed\x51\x56\x5c\xb6\xed\x6c\x63\x72\x99\x01')

    found = True
    while found:
        found = False
        for local_f4 in range(0x10):
            arg1 = (local_f4 + 1) % 0x11 + 4
            arg2 = local_f4 + 4
            if key[arg1] == -1 and key[arg2] != -1:
                found = True
                key[arg1] = foo[local_f4] ^ key[arg2]
            elif key[arg1] != -1 and key[arg2] == -1:
                found = True
                key[arg2] = foo[local_f4] ^ key[arg1]

    key.extend(b'\x20\xc2\xaf\x5c\x5f\x28\xe3\x83\x84\x29\x5f\x2f\xc2\xaf\x20\x74')

    s = 0
    for i in [0x28, 0x55, 0x83, 0xb0, 0xd7, 0x4b, 0x74]:
        k = (i - s) & 0xff
        s += k
        key.append(k)

    flag = 'cd21{' + bytearray(key).decode('utf8') + '}'
    return flag


if __name__ == "__main__":
    print(solve())
