When I checked in, I noticed a yellow stain on the bed sheet. After the 4th day, I noticed the yellow stain still on the bed sheet (the bed sheet hadn't been changed for 3 days). After getting angry with the receptionist, the cleaning service staff told me to change it immediately. If I hadn't noticed the yellow stain, I wouldn't have known the bed sheet hadn't been changed because the bed sheet had been tidied up again.