public int findMostFrequent() {
        ArrayList<Integer> array = new ArrayList<>();

        for (int[] line : matrix) {
            for (int el : line){
                array.add(el);
            }
        }

        Collections.sort(array);

        int maxCount = 0;
        int num = 0;
        for (int j : array) {
            int kol = 0;
            for (int value : array) {
                if (j == value) {
                    kol++;
                }
                if (kol > maxCount) {
                    maxCount = kol;
                    num = j;
                }
            }
        }

        return num;
    }