N = int(input())
lsA = list(map(int,input().split()))
lsA1 = []
lsA2 = []
for i in range(N):
    if i%2==0:
        lsA1.append(lsA[i])
        lsA2.append(lsA[i]^1)
    else:
        lsA1.append(lsA[i]^1)
        lsA2.append(lsA[i])

lsA1.append(0)
lsA2.append(0)
lsA1G = [0]*(N+1)
lsA2G = [0]*(N+1)
max1 = N-1
max2 = N-1
for i in range(N-1,-1,-1):
    if lsA1[i]==0:
        max1 = i
    if lsA2[i]==0:
        max2 = i
    lsA1G[i] = max1
    lsA2G[i] = max2
ans = 0
for i in range(N-1):
    if i%2==0:
        ans += lsA1G[i]-i
    else:
        ans += lsA2G[i]-i
print(ans)