import sys
#input = sys.stdin.readline #文字列につけてはダメ
input = sys.stdin.buffer.readline #文字列につけてはダメ
#sys.setrecursionlimit(1000000)
#import bisect
#import itertools
#import random
#from heapq import heapify, heappop, heappush
#from collections import defaultdict
#from collections import deque
#import copy

#かなり実装難しい。★2ではないでしょ。

def main():
    N = int(input())
    A = [0] + list(map(int,input().split()))
    B = []
    ans = 0
    temp = []
    for i in range(1,N+1):
        if A[i] == 0:
            if A[i-1] == 1:
                temp.append(A[i])
            else:
                B.append(temp)
                temp = []
        else:
            if A[i-1] == 0:
                temp.append(A[i])
            else:
                B.append(temp)
                temp = [A[i]]
    if temp:
        if temp[-1] == 0:
            ans -= len(temp)//2
        else:
            ans -= (len(temp)+1)//2
    B.append(temp)
    #print(ans)

    for i in range(len(B)):
        if len(B[i])%2 == 1:
            x = (len(B[i])+1)//2
            ans += x**2
        else:
            x = len(B[i])//2
            ans += (1+x)*x
        #print(ans)
    print(ans)


        


if __name__ == '__main__':
    main()