from collections import defaultdict

N = int(input())
A = list(map(int,input().split()))
dic = defaultdict(int)
for x in A:
    dic[x] += 1

ans = N*(N-1)//2 #すべて1

ones = dic[1]*(dic[1]-1)//2
ans += ones

onetwo = dic[1]*dic[2]
ans += onetwo * 2

oneelse = dic[1]*(N - dic[1] - dic[2])
ans += oneelse

print(ans)