n = int(input())
A = list(map(int, input().split()))
one = 0
two = 0
for a in A:
    if a == 1:
        one += 1
    elif a == 2:
        two += 1
x = n - one
ans = x * (x - 1) // 2
ans += 2 * one * (one - 1) // 2
ans += 3 * one * two
print(ans)