A teenage boy walks into a shop. He says to the shopkeeper "Can I have a pack of condoms please." The boy just gives the man the money, and walks off, bursting out laughing, leaving the pack of condoms behind.
The next day, the boy does exactly the same thing at the shop. And the next day. After the third day, when the boy had left bursting out laughing, having given the shopkeeper the money but leaving the pack of condoms behind, the shopkeeper says to an assistant "If that boy does the same thing tomorrow, I want you to follow him when he leaves."
So, the next day the boy did do the same thing. But this time, the shopkeeper's assistant followed him whilst the boy was on his way home. The assistant cam back after an hour or less. The shopkeeper said "Well? Where did he go?" The assistant looked at him and said "Your house."