from bisect import bisect_left, bisect_right
N = int(input())
A = list(map(int, input().split()))
K = [[] for _ in range(N)]
for i in range(N):
    for j in range(i+1,N):
        if A[i]+10 == A[j]:
            K[i].append(j)
T = []
ans = 0
for i in range(N):
    T += K[i]
    T.sort()
    for j in range(i+1,N):
        if A[i]+1 == A[j]:
            l = bisect_right(T, i)
            r = bisect_left(T, j)
            ans += r-l
print(ans)