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

L = []
R = []
l = {}
for a in A:
    L.append(l.copy())
    l[a] = l.get(a, 0) + 1

r = {}
for a in A[::-1]:
    R.append(r.copy())
    r[a] = r.get(a, 0) + 1

R = R[::-1]
ans = 0
for l in range(n):
    for r in range(l + 1, n):
        if A[r] >= A[l]:
            continue
        ans += L[l].get(A[r] - 10, 0) * R[r].get(A[l] + 1, 0)
print(ans)