Charlie borrowed $50 from Andy and $50 from Ben.

Charlie then used the $100 to buy something worth $97 and received $3 change.

He then return $1 to Andy and $1 to Ben and kept $1 to himself.

He now owes Andy $49 and Ben $49 but with Andy's $49 and Ben's $49 and his own $1,the total is only $99.

Where did the other $1 go to?