const FACTORIALS: [u64; 21] = [
    1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880,
    3628800, 39916800, 479001600, 6227020800,
    87178291200, 1307674368000, 20922789888000,
    355687428096000, 6402373705728000,
    121645100408832000, 2432902008176640000,
];

fn factorial_table(n: u64) -> u64 {
    FACTORIALS[n as usize]
}