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

B = []
for i, a in enumerate(A):
    if i%2 == 1:
        B.append(1-a)
    else:
        B.append(a)

pre = n
cur = -1
C = [0]*n
for i in reversed(range(n)):
    if B[i] != cur:
        pre = i
        cur = B[i]
    C[i] = pre+1

ans = 0
for i, a in enumerate(A):
    if a:
        ans += min(C[i], n-1)-i
print(ans)