n = int(input())
A = list(map(int, input().split()))
for i in range(1, n, 2):
    A[i] ^= 1
    
r = n - 2
ans = 0
for i in range(n - 2, -1, -1):
    if A[i] != A[i + 1]:
        r = i
    if i % 2 != A[i] % 2:
        ans += r - i + 1
print(ans)