from collections import defaultdict


N = int(input())
A = list(map(int, input().split()))
di = defaultdict(list)
for i in range(N):
    di[A[i]].append(i)
ans = 0
for i in range(N - 3):
    for j in range(i + 1, N - 2):
        for k in di[A[i] + 10]:
            if A[k] > A[j]:
                break
            for l in di[A[j] + 1]:
                if (
                    A[i] + 10 == A[k]
                    and A[j] + 1 == A[l]
                    and A[i] < A[j]
                    and A[j] > A[k]
                    and A[k] < A[l]
                    and i < j < k < l
                ):
                    ans += 1
print(ans)