alert when selected similar value from multiple check box with same classs anem

When I select second time from below check box with same value should alert 'value is already checked' how to do that using jquery?

<div>
    <input type="checkbox" class="check" value="1"/>
</div>
<div>
    <input type="checkbox" class="check" value="2"/>
</div>
<div>
    <input type="checkbox" class="check" value="1"/>
</div>
<div>
    <input type="checkbox" class="check" value="3"/>
</div>
<div>
    <input type="checkbox" class="check" value="4"/>
</div>
<div>
    <input type="checkbox" class="check" value="3"/>
</div>

I tried with below code but nothing is working

var itemVal=false;

    $(document).on('change','.check:checked',function(){

            selVal=$(this).val();

            $('.check:checked').each(function(){

                if($(this).val()==selVal){
                    itemVal=true
                }

            })

            if(itemVal==true){

            alert('Proceed')
            }else{

            alert('Please choose same name')
            }






    })



    })