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

cum = [[0]*(N+1) for _ in range(2000)]
for i, a in enumerate(A):
    cum[a-1][i+1] += 1
for i in range(2000):
    for j in range(1, N+1):
        cum[i][j] += cum[i][j-1]

ans = 0
for i in range(1, N-2):
    for j in range(i+1, N-1):
        if A[i] <= A[j]:
            continue
        k = A[i]-A[j]
        l = A[i]-k-10
        r = A[j]+k+1
        if 1 <= l <= 2000 and 1 <= r <= 2000:
            ans += cum[l-1][i]*(cum[r-1][-1]-cum[r-1][j+1])

print(ans)