Popup menu not working inside modal window?

Question

css

Hello. Inserted into the body of the modal window an input field with add. options.
If you write manually in the control, everything is fine, but if you select options
from the drop-down list, then the selected ones are not substituted in the input.
Everything works fine without the modal window. Everything inside is bad.
I think the solution can be very simple. Thanks in advance!!!

<div class="container">
<div class="modal fade" id="modal" role="dialog">
        <div class="modal-dialog modal-sm">
            <div class="modal-content">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal">&times;</button>
                    <h4 class="modal-title">Изменить данные?</h4>
                </div>
                <div class="modal-body ">
                    <div class="input-group input-group-sm fast-field"
                         data-container-for="kto_schitaet">
                        <input class="form-control" id="kto_schitaet" >
                        <div class="input-group-btn">
                            <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown">
                                <span class="caret"></span>
                            </button>
                            <ul class="dropdown-menu" role="menu">
                                <li ><a href="#" class="input-option" >variant 1</a></li>
                                <li ><a href="#" class="input-option" >variant 2</a></li>
                            </ul>
                        </div>
                    </div>







                </div>
                <div class="modal-footer">
                    <button type="button" class="btn btn-default"
                            id="modal-submit-button"
                            data-dismiss="modal">изменить</button>
                </div>
            </div>
        </div>
    </div>

Answer 1

I have all the norms displayed, but how should the option be inserted from clicking on it into the input? do you have js code or what? i see data- but how should it bind without js?