use std::io::Read;

fn fact(n: u128) -> u128 {
	if n == 0 { 1 }
	else { n * fact(n - 1) }
}

fn main() {
	let mut s = String::new();
	std::io::stdin().read_to_string(&mut s).ok();
	let mut itr = s.trim().split_whitespace();
	let n: usize = itr.next().unwrap().parse().unwrap();
	let a: Vec<usize> = itr.map(|e| e.parse::<usize>().unwrap() - 1).collect();
	let mut c = vec![0usize; n];
	for i in 0..n { c[a[i]] += 1; }
	let mut ans = fact(n as u128);
	for i in c{
		if i > 0 { ans /= fact(i as u128) }
	}
	println!("{}", ans);
}