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

a_reverse = a[::-1]
num = [0]*n
check = [True]*n
cnt = 0
ans = 0
for i in range(n-1):
    # cnt = 0
    if a_reverse[i] != a_reverse[i + 1]:
        cnt += 1
        check[i + 1] = check[i]
    else:
        cnt = 0
        check[i + 1] = False
    if a_reverse[i + 1]:
        num[i + 1] = cnt

for i in range(1, n):
    if a_reverse[i] and not check[i]:
        ans += 1

# print(*a_reverse)
# print(*num)
# print(*check)
print(sum(num) + ans)