class SegmentTree:
  def __init__(self, n, p, unit, f):
    self.num = 2**((n-1).bit_length())
    self.seg = [unit]*(2*self.num)
    for i in range(n):
      self.seg[i+self.num] = p[i]
    for i in range(self.num-1, 0, -1):
      self.seg[i] = f(self.seg[i << 1], self.seg[(i << 1)+1])
    self.f = f
    self.unit = unit

  def update(self, i, x):
    i += self.num
    self.seg[i] = x
    while i:
      i >>= 1
      self.seg[i] = self.f(self.seg[i << 1], self.seg[(i << 1)+1])

  def query(self, l, r):
    ansl = ansr = self.unit
    l += self.num
    r += self.num-1
    if l == r:
      return self.seg[l]
    while l < r:
      if l & 1:
        ansl = self.f(ansl, self.seg[l])
        l += 1
      if ~r & 1:
        ansr = self.f(self.seg[r], ansr)
        r -= 1
      l >>= 1
      r >>= 1
    if l == r:
      ansl = self.f(ansl, self.seg[l])
    return self.f(ansl, ansr)

def f(x,y):
  xm1,xm2,xM=x
  ym1,ym2,yM=y
  M=max(xM,yM)
  if xm1<ym1:
    m1=xm1
    m2=min(ym1,xm2)
  else:
    m1=ym1
    m2=min(xm1,ym2)
  return (m1,m2,M)

n=int(input())
p=list(map(int,input().split()))
seg=SegmentTree(n,[(i,10**9,i)for i in p],(10**9,10**9,0),f)
ans=0
for l in range(n-2):
  for r in range(l+2,n):
    m1,m2,M=seg.query(l,r+1)
    if M<=m1+m2:
      ans+=1
print(ans)