N = int(input())
A = list(map(int,input().split()))
ans = 0
flag = 0
cnt = 0
for i in range(N):
    if A[i]==1-flag:
        cnt += 1
        flag = 1-flag
    else:
        m = (cnt+1)//2
        if cnt%2==0:
            ans += m*(m+1)
        else:
            ans += m*m
        flag = A[i]
        cnt = flag
m = (cnt+1)//2
if cnt%2==1:
    ans += m*(m-1)
else:
    ans += m*m
print(ans)