n = int(input())
a = list(map(int, input().split()))
one = a.count(1)
two = a.count(2)
ans = 0
ans += 3*one*two
ans += 2*one*(one-1)//2
ans += 2*one*(n-one-two)
ans += (n-one)*(n-one-1)//2
print(ans)