import sys
input = sys.stdin.readline
from collections import Counter

N=int(input())
A=list(map(int,input().split()))

C=Counter(A)

ONE=C[1]
TWO=C[2]

ANS=N*(N-1)//2
ANS+=ONE*(N-1)-ONE*(ONE-1)//2
ANS+=ONE*TWO

print(ANS)