"""

"""

import sys
from sys import stdin

N = int(stdin.readline())

A = list(map(int,stdin.readline().split()))

dp = [[0,0] for i in range(N)]

for i in range(N-2,-1,-1):

    for turn in range(2):

        now = A[i] ^ turn
        if now == 1:
            dp[i][turn] = dp[i+1][turn^1] + 1

ans = 0
for i in range(N):
    ans += dp[i][0]
print (ans)