DWang: a friend of mine
DWang: used 3 minutes on his phone last month
DWang: but he got refunded 4!
DWang: the phone company apparently uses 4-byte unsigned ints
DWang: because it UNDERFLOWED
DWang: he apparently used 2^32 minutes at 10 cents a minute
DWang: so he got a bill
DWang: for $430 MILLION