from collections import defaultdict
N = int(input())
A = list(map(int,input().split()))
X = defaultdict(int)
ans = 0
for i in range(1,N-2):
  X[A[i-1]] += 1
  Y = defaultdict(int)
  for j in range(i+1,N-1):
    l = N - 2 - j + i + 1
    Y[A[l+1]] += 1
    b = A[i]
    c = A[l]
    k = b - c
    a = b - k - 10
    d = c + k + 1
    p = X[a]
    q = Y[d]
    ans += p*q
print(ans)