# import pypyjit;pypyjit.set_param("max_unroll_recursion=-1")
# from bisect import *
# from collections import *
# from heapq import *
# from itertools import *
# from math import *
# from datetime import *
# from decimal import *  # PyPyだと遅い
# from string import ascii_lowercase,ascii_uppercase
# import numpy as np
import sys

# import os

# sys.setrecursionlimit(10**6) # PyPyだと遅い
# INF = 10**18
# MOD = 998244353
# MOD = 10**9 + 7
# isFile = os.path.exists("input.txt")
File = open("input.txt", "r")


def input():
    return File.readline()[:-1]


# ///////////////////////////////////////////////////////////////////////////


N = int(input())
A = list(map(int, input().split()))
countList = [[0] * 2001 for _ in range(N)]

for i in range(-1, -N - 1, -1):
    for j in range(2001):
        countList[i][j] = countList[i + 1][j]
    countList[i][A[i]] += 1

ans = 0
for i in range(N):
    for j in range(i + 1, N):
        diff = A[j] - A[i] - 10
        if diff <= 0:
            continue
        for k in range(j + 1, N):
            if A[k] == A[j] - diff and A[k] + diff + 1 < 2001:
                ans += countList[k][A[k] + diff + 1]

print(ans)