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<form action="{{action('CuentaController@asignar')}}" method="post">

                  <select name="valor" id="valor" class=" form-control"  value="{{ old('tipo') }}" required>
                        @foreach($usuariosOpciones as $user_id => $usuario_ad)
                          <option value="{{ $user_id }}">{{ $usuario_ad }}</option>
                       @endforeach
                   </select>

                   {{csrf_field()}}
                   <button class="btn btn-danger btn-xs" type="submit"><span class="glyphicon glyphicon-plus-sign"></span></button>
                   </form>

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