N=int(input())
A=list(map(int, input().split()))
aa=max(A)+10;ans=0
for k in range(1,max(A)+1):
  dp1=[0]*aa;dp2=[0]*aa;dp3=[0]*aa;dp4=[0]*aa
  x,y,z=k+1,-k,k+10
  for a in A:
    if aa>a-x>0:
      dp4[a]+=dp3[a-x]
    if aa>a-y>0:
      dp3[a]+=dp2[a-y]
    if aa>a-z>0:
      dp2[a]+=dp1[a-z]
    dp1[a]+=1 
  ans+=sum(dp4)
print(ans)