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

b0 = a[:]
b1 = a[:]

for i in range(n):
    if i % 2 == 0:
        b0[i] ^= 1
    else:
        b1[i] ^= 1

nxt0 = [n - 1] * n
nxt1 = [n - 1] * n
for b, nxt in ((b0, nxt0), (b1, nxt1)):
    x = n - 1
    for i in range(n)[::-1]:
        nxt[i] = x
        if b[i] == 1:
            x = i

ans = 0
for i in range(n):
    if a[i] == 0:
        continue
    if i % 2 == 0:
        ans += nxt0[i] - i
    else:
        ans += nxt1[i] - i
print(ans)