n=int(input())
a=list(map(int,input().split()))
ans=0
cnt2=0
for i in range(n):
    if a[i]==0:
        ans+=n-i
    else:
        cnt2=max(cnt2,i)
        for j in range(cnt2,n):
            if a[j]==0:
                cnt2=j
                ans+=n-j
                break
        else:
            cnt2=n
print(ans)