# YC1765
N = int(input())
A = list(map(int,input().split()))

ans = 0
t = 0
for i in reversed(range(N-1)):
    if A[i] == 0:
        if A[i+1] == 1:
            t += 1
        else:
            t = 1
    else:
        if A[i+1] == 0:
            t += 1
            ans += t
        else:
            t = 1
            ans += 1
print(ans)