import bisect

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

B = [i for i, e in enumerate(A) if e == 0]

ans = 0
for i in range(n):
    t = 0
    if A[i] == 0:
        t = n - i
    else:
        if bisect.bisect_left(B, i) < len(B):
            t = n - B[bisect.bisect_left(B, i)]
    ans += t

print(ans)