#!/usr/bin/env python3
import sys
from bisect import bisect_left, bisect_right, insort_left, insort_right  # type: ignore
from collections import Counter, defaultdict, deque  # type: ignore
from math import gcd, sqrt, ceil  # type: ignore
from heapq import heapify, heappop, heappush, heappushpop, heapreplace, merge  # type: ignore
from itertools import accumulate, combinations, permutations, product  # type: ignore
from string import ascii_lowercase, ascii_uppercase # type: ignore

def LI(): return list(map(int, sys.stdin.buffer.readline().split()))
def I(): return int(sys.stdin.buffer.readline())
def LS(): return sys.stdin.buffer.readline().rstrip().decode("utf-8").split()
def S(): return sys.stdin.buffer.readline().rstrip().decode("utf-8")
def IR(n): return [I() for _ in range(n)]
def LIR(n): return [LI() for _ in range(n)]
def SR(n): return [S() for _ in range(n)]
def LSR(n): return [LS() for _ in range(n)]
def SRL(n): return [list(S()) for _ in range(n)]

N = I()
A = LI()
num = [[] for _ in range(2010)]
cnt = [[0]*(N+1) for _ in range(2010)]
for i,a in enumerate(A):
    num[a].append(i)
    for j in num[a-1]:
        cnt[a-1][j]+=1
        cnt[a-1][i]-=1

for i in range(2010):
    cnt[i] = list(accumulate(cnt[i]))
for i in range(2009,0,-1):
    for j in range(N+1):
        cnt[i-1][j] += cnt[i][j]

ans = 0
for i in range(N):
    a1 = A[i]
    for k in num[a1+10]:
        if k-i<2: continue
        a3 = A[k]
        # if cnt[a3+1][k]>0:
        #     print(i,k,cnt[a3+1][k])
        ans += cnt[a3+1][k]
print(ans)