n = int(input())
A = list(map(int,input().split()))
zero = [n]*(n+1)
for i in range(n)[::-1]:
    if A[i] == 0:
        zero[i] = i
    else:
        zero[i] = zero[i+1]
ans = 0
for i in range(n):
    ans += n-zero[i]
print(ans)