from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline

N = int(input())
A = list(map(int,input().split()))
M = max(A)
def f(k):
    
    
    dp = [[0]*(M+2) for _ in range(4)]
    a = A[0]
    dp[0][a] = 1
    for i in range(N-1):
        a = A[i+1]
        if a>=k+1:
            dp[3][a] += dp[2][a-k-1]
        if a <= M - k:
            dp[2][a] += dp[1][a+k]
        if a>=k+10:
            dp[1][a] += dp[0][a-k-10]
        dp[0][a] += 1
    return sum(dp[3])
ans = 0
for k in range(1,M+1):
    ans += f(k)
print(ans)