Try to solve this mathematic...

Pete and Larry had not seen each other in many years. Now they had a long talk trying to fill in the gap of those years by telling about their lives. Finally Pete invited Larry to visit him in his new apartment.
"I've got a wife and three kids and I'd love to have you visit us."
"Great. Where do you live?"
"Here's the address. And there's plenty of parking behind the apartment. Park and come around to the front door, kick it open with your foot, go to the elevator and press the button with your left elbow, then enter! When you reach the sixth floor, go down the hall until you see my name on the door. Then press the doorbell with your right elbow and I'll let you in."
"Good. But tell me...what is all this business of kicking the front door open, then pressing elevator buttons with my right, then my left elbow?"
"Surely, you're not coming empty-handed."