import sys 
from collections import Counter
def main():
    N = int(input())
    A = list(map(int,input().split()))
    MAX = 2*pow(10,5) + 1000
    S = [0]
    for i in range(1,MAX):
        temp = S[-1] + i
        S.append(temp)
    ans = S[N]
    cnt = 0
    for i in range(N):
        if A[i] == 0:
            ans -= S[cnt]
            cnt = 0
        else:
            cnt += 1
    ans -= S[cnt]
    print(ans)

if __name__ == '__main__':
    main()