One man went to his family doctor, he asked:"doctor, I will to get married, but i and my girlfriend is the first time, you can tell us how to do?" doctor watching he grew up,and hear this question feel a little uncomfortable then looked outside and said: "Look over there,you see the park there are two dogs ? see what they are doing it? followed do it at the home." Two months later, they met again, the doctor asked:"how about sex life? man replied:"very well,but really do in the park is a bit cold,and there are some people peep."