import pypyjit
pypyjit.set_param('max_unroll_recursion=-1')
def count_asakatsu_subsequences(N, A):
    cnt = 0
    indices = {}
    for i, a in enumerate(A):
        if a not in indices:
            indices[a] = []
        indices[a].append(i)
    for i in range(N - 3):
        for j in range(i + 1, N - 2):
            k = A[j] - A[i] - 10
            if k > 0:
                m_values = indices.get(A[j] - k, [])
                for m in m_values:
                    if m > j:
                        n_values = indices.get(A[m] + k + 1, [])
                        for n in n_values:
                            if n > m:
                                cnt += 1
    return cnt

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


result = count_asakatsu_subsequences(N, A)


print(result)