n = int(input())
a = list(map(int, input().split()))
a.append(0)

s = a[0]
k = 0
nc = 0

for i in range(n + 1):
    if s == 0 and a[i] == 0:
        nc += (i - k)*(i - k + 1)/2
        s = 1
        continue
    if s == 1 and a[i] == 1:
        k = i
        s = 0

print(int(n * (n + 1) / 2 - nc))