/**
knakul853
**/
class Solution {
public:
    int fourSumCount(vector<int>& A, vector<int>& B, vector<int>& C, vector<int>& D) {

        int n = (int)A.size();

        unordered_map<int,int>mp;
        for( int i=0;i<n;i++ )
        {
            for(int j=0;j<n; j++ )
            {
                mp[A[i] + B[j]]++;
            }
        }

        int ans = 0;

         for( int i=0;i<n;i++ )
        {
            for(int j=0;j<n; j++ )
            {
              if(mp.count(-C[i]-D[j]))ans+=mp[-C[i]-D[j]];
            }
        }
        return ans;


    }
};