from sys import stdin
n, *a = map(int, stdin.read().split())

ans = 0
renzoku = 0
last = 1
for i in range(n-1):
    if a[i] == 1:
        if last == 1:
            renzoku = 0
        renzoku += 1
    else:
        if last == 0:
            renzoku = 0
    ans += renzoku
    last = a[i]

print("{}".format(ans))