Calculate the number 863

A woman takes her 16-year-old daughter to the doctor. "Okay, Mrs. Jones, what's the problem?"The mother says, "It's my daughter, Debbie. She keeps getting these cravings, she's putting on weight, and she is sick most mornings." The doctor gives Debbie a good examination, then turns to the mother and says, "Well, I don't know how to tell you this, but your Debbie is pregnant--about four months would be my guess."The mother says, "Pregnant?! She can't be, she has never been left alone with a man! Have you, Debbie?" Debbie says, "No mother! I've never even kissed a man!" The doctor walked over to the window and stared outside. About five minutes passed before the mother said, "Is there something wrong out there, doctor?" The doctor replied, "No, not at it. It's just that the last time anything like this happened, a star appeared in the east and three wise men came over the hill. I'm not going to miss it this time around!"