-1 0 1 2 -1 -4

2

nums=sorted(map(int,input().split()))
n=len(nums); count=0
for i in range(n-2):
    if i>0 and nums[i]==nums[i-1]: continue
    l,r=i+1,n-1
    while l<r:
        s=nums[i]+nums[l]+nums[r]
        if s==0:
            count+=1
            while l<r and nums[l]==nums[l+1]: l+=1
            while l<r and nums[r]==nums[r-1]: r-=1
            l+=1; r-=1
        elif s<0: l+=1
        else: r-=1
print(count)