fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();
    let mut a = String::new();
    std::io::stdin().read_line(&mut a).ok();
    let a: Vec<usize> = a.trim().split_whitespace().map(|s| s.parse::<usize>().unwrap()-1).collect();

    let mut cnts = vec![0usize; n];
    for i in 0..n { cnts[a[i]] += 1; }
    let mut result = (1..=n as u128).fold(1u128, |x, y| x * y);
    for i in 0..n {
        if cnts[i] > 0 {
            result /= (1..=cnts[i] as u128).fold(1u128, |x, y| x * y);
        }
    }
    println!("{}", result);
}