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

class UnionFind(object):
    def __init__(self, n=1):
        self.par = [i for i in range(n)]
        self.rank = [0 for _ in range(n)]
        self.size = [1 for _ in range(n)]
    def find(self, x):
        """
        x が属するグループを探索して親を出す。
        """
        if self.par[x] == x:
            return x
        else:
            self.par[x] = self.find(self.par[x])
            return self.par[x]
    def union(self, x, y):
        """
        x と y のグループを結合
        """
        x = self.find(x)
        y = self.find(y)
        if x != y:
            if self.rank[x] < self.rank[y]:
                x, y = y, x
            if self.rank[x] == self.rank[y]:
                self.rank[x] += 1
            self.par[y] = x
            self.size[x] += self.size[y]
    def is_same(self, x, y):
        """
        x と y が同じグループか否か
        """
        return self.find(x) == self.find(y)
    def get_size(self, x):
        """
        x が属するグループの要素数
        """
        x = self.find(x)
        return self.size[x]


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


        


if __name__ == '__main__':
    main()