from bisect import *
N = int(input())
A = list(map(int,input().split()))
from collections import defaultdict
dic = defaultdict(list)
for i,a in enumerate(A):
    dic[a].append(i)
ans = 0
for i in range(N - 3):
    a = A[i]
    for j in range(i + 1,N - 2):
        b = A[j]
        if b - a < 10:
            continue
        if dic[a+10]:
            for k in dic[a + 10]:
                if i < j < k:
                    if dic[b + 1]:
                        ans += len(dic[b + 1]) - bisect_left(dic[b + 1],k)

print(ans)