import sys
sys.setrecursionlimit(10 ** 6)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LC(): return list(input())
def IC(): return [int(c) for c in input()]
def MI(): return map(int, sys.stdin.readline().split())
INF = float('inf')
MOD = 10**9 + 7
def solve():
    N = II()
    A = LI()
    Ans = 0
    for l in range(N):
        r = N-l-1
        if(A[l] == 0):
            #0を発見した場合
            R = 0
            for r in range(l+1,N):
                #次の0までの1の個数を数える
                if(A[r] == 1):
                    R+=1
                else:
                    break
            #print(l,R)
            Ans += (l+1)*(R+1)
    print(Ans)
    return
solve()