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

L = [[0 for _ in range(2001)] for _ in range(N+1)]
R = [[0 for _ in range(2001)] for _ in range(N+1)]

for i in range(N):
    for j in range(2001):
        L[i+1][j] = L[i][j]
    L[i+1][A[i]] += 1

for i in range(N, 0, -1):
    for j in range(2001):
        R[i-1][j] = R[i][j]
    R[i-1][A[i-1]] += 1

ans = 0
for i2 in range(1, N-2):
    for i3 in range(i2+1, N-1):
        k = A[i2]-A[i3]
        if k<=0:
            continue
        a1 = A[i2]-k-10
        a4 = A[i3]+k+1
        ans += L[i2][a1] * R[i3+1][a4]
print(ans)