import bisect

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

D = dict()
for i in range(1, N):
    if A[i] not in D:
        D[A[i]] = [i]
    else:
        D[A[i]].append(i)

ans = 0
for i2 in range(1, N):
    a2 = A[i2]
    for i1 in range(i2):
        a1 = A[i1]
        k = a2-a1-10
        if k<=0:
            continue
        
        a3 = a2-k
        if a3 not in D:
            continue
        pos = bisect.bisect_left(D[a3], i2+1)
        if pos==N:
            continue
        a4 = a3+k+1
        if a4 not in D:
            continue
        for j in range(pos, len(D[a3])):
            i3 = D[a3][j]
            pos2 = bisect.bisect_left(D[a4], i3+1)
            ans += len(D[a4])-pos2
print(ans)