Grandpa and Viagra

Grandpa and Little Johnny are sitting on a bench in the park. Johnny asked, "Grandpa, are you going to take that new Viagra?"

Grandpa looks at him and says, "No Johnny, I will not."

"But Grandpa, why?" asks little Johnny.

Grandpa replies, "Because there is no sense in putting lead in your pencil if you have no one worth writing to."