func main()
	var n: int :: cui@inputInt()
	var a: []int :: #[n]int
	var map: dict<int, int> :: #dict<int, int>
	for i(0, n - 1)
		do a[i] :: cui@inputInt()
		do map.add(a[i], map.get(a[i], &) + 1)
	end for
	
	var ans: int :: n * (n - 1) / 2
	var n1: int :: map.get(1, &)
	var n2: int :: map.get(2, &)
	do ans :+ n1 * (n1 - 1) / 2
	do ans :+ n1 * n2 * 2
	do cui@print("\{ans}\n")
end func