import bisect
import itertools

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

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

ans = 0
a1a3 = set()
for a1 in D.keys():
    a3 = a1+10
    if a3 not in D:
        continue
    for p in itertools.product(D[a1], D[a3]):
        if p[0]>=p[1]:
            continue
        a1a3.add(p)

a2a4 = set()
for a2 in D.keys():
    a4 = a2+1
    if a4 not in D:
        continue
    for p in itertools.product(D[a2], D[a4]):
        if p[0]>=p[1]:
            continue
        a2a4.add(p)

for i1, i3 in a1a3:
    for i2, i4 in a2a4:
        k = A[i2]-A[i1]-10
        if k<=0:
            continue
        if i1<i2<i3<i4:
            ans+=1

print(ans)