Two men sat together in a compartment on the Trans-Siberian Express. The ride was long and noisy, but the men were engrossed with their laptops. After a few hours the first man drew a pack of cigarettes out of his pocket and offered them to the second man.
"Cigarette?" said the second man. "I tried one once…didn't really enjoy it. But, please, you go right ahead."
The first man smoked in silence and the train rumbled on for several more hours. Eventually, the first man opened his suitcase and brought out a bottle of vodka, offering some to his traveling companion.
"Vodka?" said the second man. "I tried it once…didn't really enjoy it. But, please, you go right ahead."
The first man sipped slowly at the vodka and stared out at the fat snowflakes falling past the train window, then returned to his laptop. After several more hours he looked up, alarmed. "I'm getting a funny error message." he said. "Do you think I could have a virus?"
"Virus?" said the second man. "I had one once. My son took care of it for me…. You know, he's in the next compartment. He's good with PCs. You might like to ask him to take a look."
"Excuse me," said the first man after a pause. "Do you by any chance have only one son?"