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

All = [0] * 2001
for a in A:
    All[a] += 1

ans = 0
for i in range(N - 3):
    right = All[:]
    left = [0] * 2001
    right[A[i]] -= 1
    right[A[i + 1]] -= 1
    line = 0
    for j in range(i + 2, N - 1):
        right[A[j]] -= 1
        line -= left[A[j] - 1]
        left[A[j - 1]] += 1
        line += right[A[j - 1] + 1]
        if A[i] + 10 == A[j]:
            ans += line
    All[A[i]] -= 1
print(ans)