import sys
input = sys.stdin.readline
def iinput(): return int(input())
def sinput(): return input().rstrip()
def i0input(): return int(input()) - 1
def linput(): return list(input().split())
def liinput(): return list(map(int, input().split()))
def miinput(): return map(int, input().split())
def li0input(): return list(map(lambda x: int(x) - 1, input().split()))
def mi0input(): return map(lambda x: int(x) - 1, input().split())
INF = 10**20
MOD = 1000000007

N = iinput()
A = ''.join(linput())

tmp = '1'
seq = ''
for i in range(N):
    seq += tmp
    if tmp == '1':
        tmp = '0'
    else:
        tmp = '1'
ans = 0
for i in range(1, N+1):
    tmp = seq[:i]
    ans += A.count(tmp)
    if A[-len(tmp):] == tmp:
        ans -= 1
print(ans)