Given $1, $5, $20, and $100 dollar bills, what is the fewest number of bills needed to form amounts ranging from $1 to $100? For example, $4 would require four $1 bills. Bills can be reused, so the number is not cumulative. What is the minimum number of bills you must have to always provide exact change for both a transaction of $x and $(100-x), where x < 100?