Fetch Record of Maximum Value **(Coredata)**
===

I am new to Core Data,I am trying to fetch a record which has maximum Timestamp value.
In Following code I am getting the maximum TimeStamp value but I want that record that has maximum timestamp value.

AppDelegate *appDelegate =  (AppDelegate *)[[UIApplication sharedApplication] delegate];

    NSManagedObjectContext *context = [appDelegate managedObjectContext];
    
    NSEntityDescription *entity = [NSEntityDescription
                                   entityForName:@"EnergyCumulative" inManagedObjectContext:context];
  
   
    NSFetchRequest *fetchRequest = [[ NSFetchRequest alloc] init];
    [fetchRequest setEntity:entity];
    NSExpression *keyPathExpression = [NSExpression
                                       expressionForKeyPath:@"TimeStamp"];
    NSExpression *ex = [NSExpression expressionForFunction:@"max:" 
                                                 arguments:[NSArray arrayWithObject:keyPathExpression]];
    
    
    NSExpressionDescription *expressionDescription = [[NSExpressionDescription alloc] init];
    [expressionDescription setName:@"AvgReading"];
    [expressionDescription setExpression:ex];
    [expressionDescription setExpressionResultType:NSStringAttributeType];
    
    [fetchRequest setPropertiesToFetch:[NSArray arrayWithObject:expressionDescription]];
    [fetchRequest setResultType:NSDictionaryResultType];
    [fetchRequest setEntity:entity];
    
       
    NSError *error;  
   
    NSArray *tripArray = [context executeFetchRequest:fetchRequest error:&error];
     NSLog(@"%@",tripArray);  

In NSLog I am getting
(
        {
        AvgReading = 1342704600000;
    }
)