input()
n=input()[:-1].replace(" ","")
ans=0
f=0
d=1
for i in range(len(n)):
    b = n[i]
    if b == "1":
        if f == "1":
            d = 1
        ans += d
    else:
        if f == "1":
            ans += d
            d += 1
        else:
            d = 1
    f = b
print(ans)