validation doesnt work in one instance - html

Question

I have a dropdown in which when I select 'one' only then my input appears. That input is required field. What I want is when user select 'one' only then validation on the input works and hence on save button it shows error but if it selects other values or no value then on save it doesn't show validation error. My code is working correctly but only when I click on save button twice.If I click on the save once then it shows error even if I dont select anyone or select other one.
<form name="myForm" data-ng-submit="save(myForm.$valid)"novalidate="novalidate">
<div class="form-group">
<label class="col-md-6">Select:</label>
<select class="col-md-2" ng-model="val.value">
<option value="1" selected>one</option>
<option value="2">two</option>
<option value="3">three</option>
<option value="4">four</option>
</select>
<div ng-show="val.value=='1'">
<label class="col-md-3">one:</label>
<input type="number" class="col-md-4" ng-model="val.one" name="valOne" data-ng-class="{'has-error':myForm.valOne.$dirty && myForm.valOne.$invalid }" ng-required="val.value=='1'"/>
<div class="col-md-2" data-ng-messages="myForm.valOne.$error"
data-ng-show="myForm.valOne.$touched ||myForm.$submitted">
<div class="error-message" data-ng-message="required">Please enter Value
</div>
</div>
</div>
</div>
<button type="submit" class="btn btn-warning"><i class="fa fa-save"></i>
Save</button>
</form>
Please recommend something.