import sys
input = sys.stdin.readline
from collections import defaultdict
N=int(input())
A=list(map(int,input().split()))
cnt = defaultdict(int)
ans=0

for a in A:
    cnt[a]+=1
cntb = defaultdict(int)

for i,a2 in enumerate(A):
    cnt[a2]-=1
    cnt2 = cnt.copy()
    for j,a3 in enumerate(A):
        cnt2[a3]-=1
        if i>=j:continue
        k=a2-a3
        if k<1:continue
        a1 = a2-10-k
        a4 = a3+k+1
        ans += cntb[a1] * cnt2[a4]
    cntb[a2]+=1
print(ans)