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 = []
for a1 in D.keys():
    a3 = a1+10
    if a3 not in D:
        continue
    for i1 in D[a1]:
        for i3 in D[a3]:
            if i1+2<=i3:
                a1a3.append((i1, i3))

a2a4 = []
for a2 in D.keys():
    a4 = a2+1
    if a4 not in D:
        continue
    for i2 in D[a2]:
        for i4 in D[a4]:
            if i2+2<=i4:
                a2a4.append((i2, i4))

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)