import sys
import math
from math import sin, cos, tan
from functools import reduce
from collections import deque
import heapq
sys.setrecursionlimit(1000000)
intm1 = lambda x:int(x)-1

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

ans = 0
pre0 = -1
for i in range(N):
	if A[i] == 0:
		ans += i + 1
		pre0 = i
	else:
		if pre0 != -1:
			ans += pre0 + 1
print(ans)