#include <vector>
#include <unordered_map>
#include <algorithm>

using namespace std;

class Solution {
public:
    int cardboards(vector<int>& arr) {
        unordered_map<int, int> count;
        for (int num : arr) {
            count[num]++;
        }

        int squares = 0;
        for (auto& pair : count) {
            squares += pair.second / 4;
            pair.second %= 4;
        }

        int rectangles = 0;
        int pairs = 0;
        for (auto& pair : count) {
            pairs += pair.second / 2;
        }
        rectangles = pairs / 2;

        return abs(squares - rectangles);
    }
};