n = int(input())
A = list(map(int,input().split()))
ans = 0

M = 2001
left = [0]*M

for x in range(n):
    a2 = A[x]
    right = [0]*M

    for y in range(x,n)[::-1]:

        a3 = A[y]
        k = a2-a3
        if k <= 0:
            right[a3] += 1
            continue

        a1 = a3-10
        if a1 <= 0:
            right[a3] += 1
            continue

        a4 = a3+k+1
        if a4 < M:
            ans += left[a1]*right[a4]
        
        right[a3] += 1
    left[a2] += 1
print(ans)