How to get the apex inputfield value in the controller?

To get apex inputfield value in controller-

  public Expense_Object__c VS1 {get;set;}//This I was using already

public SaveAndReturnController(ApexPages.StandardController controller)//This 
is new
{
 VS = new Expense_Object__c();
 this.controller = controller;        
}
public PageReference saveAndReturn()
{ 
system.debug('X is:'+VS.Vegetable_Amount__c);
PageReference cancel = new 
PageReference(ApexPages.currentPage().getHeaders().get('Referer'));
insert VS;//introduced this insert
//controller.save(); I was using this previously so commented
return cancel;      
}