n = int(input())
a = list(map(int, input().split()))
b = [n - 1] * n
idx = 0
for i in range(0, n, 2):
    if a[i] == 0:
        for j in range(idx, i + 1, 2):
            b[j] = i
        idx = i + 2
idx = 1
for i in range(1, n, 2):
    if a[i] == 0:
        for j in range(idx, i + 1, 2):
            b[j] = i
        idx = i + 2
c = [n - 1] * n
idx = 0
for i in range(1, n, 2):
    if a[i] == 1:
        for j in range(idx, i, 2):
            c[j] = i
        idx = i + 1
idx = 1
for i in range(0, n, 2):
    if a[i] == 1:
        for j in range(idx, i, 2):
            c[j] = i
        idx = i + 1
ans = 0
for i in range(n):
    ans += min(b[i], c[i]) - i
print(ans)