N = int(input())
A = list(map(int, input().split()))
l, r = 0, 0
cnt = 0
while l<N:
    while r<N and A[r]!=0:
        r+=1
    if r<N:
        cnt += N-r
    if l==r:
        l+=1
        r+=1
    else:
        l+=1
print(cnt)