n = int(input())
a = list(map(int, input().split())) +[10**18]
ans = 0
for l in range(n-1):
  L = l+1
  R = n
  while R-L>1:
    m = (R+L)//2
    tmp = sorted(a[l:m+1])
    if tmp[-1] <= tmp[0]+tmp[1]:
      L = m
    else:
      R = m
  ans += L - l

print(ans)