from collections import *

N = int(input())
A = list(map(int, input().split()))
Q = deque()
for i in range(N):
    if A[i] == 0:
        Q.append(i)
        
ans = 0
for i in range(N):
    if Q:
        ans += N - Q[0]
        if Q[0] == i:
            Q.popleft()
            
print(ans)