# 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 = sys.stdin 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)