n = int(input())
a = list(map(int,input().split()))
b = a[:]
for i in range(1,n,2):
    b[i] ^= 1
b.append(-1)
pre = n
c = [0]*n
for i in range(n-1,-1,-1):
    if b[i] != b[pre]:
        pre = i
    c[i] = pre + 1

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