private int checkBox(GameBoardMark playerMark) {
        for (int k = 1; k < 8; k++) {
            for (int l = 1; l < 8; l++) {
                int cnt = 0;
                int pos = -1;
                for (int a = 0; a < 2; a++) {
                    for (int b = 0; b < 2; b++) {
                        int x = k + a + 10 * (l + b);
                        int c = gameBoard.mainBoard()[x];
                        if (c == playerMark.index) cnt++;
                        else if (c == 0) pos = x;
                    }
                }
                if (cnt == 3 && pos != -1) return pos;
            }
        }
        return GameBoard.oneMoreThanLastPositionOnBoard;
    }