package main

import . "fmt"

func main() {
	var n int
	Scan(&n)
	t := make([]int, n+1)
	c := 0
	for i := 0; i < n; i++ {
		var a int
		Scan(&a)
		if t[a] == 0 {
			c++
		}
		t[a]++
	}
	ans := 1
	for i := 1; i <= n; i++ {
		ans *= i
	}
	for _, x := range t {
		if x > 0 {
			for i := 1; i <= x; i++ {
				ans /= i
			}
		}
	}
	Println(ans)
}