OMAHA, Neb. (AP) - People are lining up for the chance at a jackpot that has now swelled to $640 million, the largest in U.S. history.

Convenience stores in 42 states and the District of Columbia are seeing a lot of customers who are dreaming about what they would do with that kind of prize -- it works out to about $347 million, after taxes, if taken as a lump sum.

A café worker in Arizona reports selling $2,600 worth of tickets to one buyer. A retired soldier in Wisconsin doubled his regular weekly ticket spending to $55.

One woman who bought $20 worth of tickets at a liquor store in downtown Washington, DC today said she's realistic about her chances -- but that since the store is around the corner from where she works, she'd be "crazy" if she didn't at least "give it a shot."

Indiana lottery officials today gave away a free Mega Millions ticket to each of the first 540 customers at several outlets around the state -- when the jackpot was still $540 million. A college student who lined up early for the freebie, and then bought five additional tickets, says he hasn't started to think about what to do with all that money.